A former federal prosecutor claimed Sunday that Rudy Giuliani's loyalty could shift as he may have to reveal 'damning secrets' about Donald Trump in order to 'save himself' after the FBI raided his home.

Renato Mariotti, who worked for the U.S. Attorney's Office for the Northern District of Illinois for nearly 10 years, penned an op/ed in Politico Sunday where he made the claims about the former president's attorney.

He noted that Trump would be unlikely to testify on behalf of Giuliani, which could further lead to the attorney outing the former president to benefit himself 'especially since he knows Trump cannot pardon him any longer.'

'The only surefire way for Trump to avoid testimony in the trial of Giuliani would be to take the Fifth, but Trump has repeatedly noted that taking the Fifth makes you look guilty,' Mariotti noted, adding that the only other way to get out of testifying is to condemn Giuliani's actions and suggest he didn't know about it.

'That would make him worthless for Giuliani as a witness and force Giuliani to point the finger at Trump to save himself,' he continued.

During his time with the Attorney's Office, Mariotti prosecuted white-collar crimes like commodities and securities fraud, health care and mortgage fraud and tax evasion.

Mariotti claims in his column that Giuliani's legal trouble could affect Trump since it reportedly centers around the attorney's efforts to lobby Trump on behalf of Ukrainian officials – the same ones who were also helping dig up dirt on then-presidential candidate Joe Biden and his family.

'At issue, as well, are Giuliani's efforts to persuade Trump to oust the ambassador to Ukraine, Marie Yovanovitch, whose anti-corruption work was viewed hostilely by those same Ukrainian officials. If Giuliani's efforts to push Trump to fire Yovanovitch were done on behalf of Ukrainian officials, that could be the sort of foreign lobbying activity that he should have disclosed,' Mariotti wrote.

LEV PARNAS AND IGOR FRUMAN

Ukrainian-born Parnas and Belarus-born Fruman are two Florida-based businessmen who helped Giuliani dig up dirt on Joe Biden and his son Hunter before the 2020 presidential election and push to remove Yovanovitch.

Federal prosecutors in Manhattan have accused Parnas and Fruman of using a shell company to make an illegal $325,000 donation to a committee supporting Trump's re-election. The men have pleaded not guilty to violating campaign finance laws and other charges. A trial is scheduled for October.

PETRO POROSHENKO

A confectionary magnate and one of Ukraine's richest men, Poroshenko took power in 2014 and served as the country's president until 2019. At Giuliani's direction, Parnas and Fruman met Poroshenko in February 2019, while he was still in office, and pressed him to announce investigations into Hunter Biden and purported Ukrainian interference in the 2016 presidential election in exchange for a state visit, the Wall Street Journal and Washington Post reported.

GYUNDUZ MAMEDOV

Mamedov, who currently serves as a high-ranking prosecutor in Ukraine, was a key intermediary in Giuliani's efforts to press Ukraine to open investigations that would tarnish Biden, according to NBC News.

He played a role in setting up a meeting between Giuliani and Ukrainian officials, NBC reported

VIKTOR SHOKIN

Shokin became Ukraine's general prosecutor in February 2015 and led an investigation into the energy company Burisma, the Ukrainian gas company where Biden's son Hunter was a board member from 2014 to 2019.

Shokin was removed from his job in 2016 following accusations of corruption by Western diplomats.

Giuliani told Reuters he met with Shokin over Skype in late 2018.

YURIY LUTSENKO

Lutsenko succeeded Shokin as general prosecutor. In 2019, Lutsenko told John Solomon, a U.S. columnist, that he had evidence related to the Bidens and Burisma. Later that year Lutsenko told Reuters he found no evidence of wrongdoing on the part of Biden’s son in his relationship with the energy firm.

Giuliani told Reuters in 2019 that he met with Lutsenko twice early that year.

KOSTIANTYN KULYK

Kulyk, a former Ukrainian prosecutor, also worked on the country's investigations into Burisma. Giuliani told Reuters he met with Kulyk in Paris in 2019.

GLIB ZAGORIY

A Ukrainian businessman and former lawmaker, Zagoriy attended a meeting between Giuliani and Lutsenko in January 2019, according to documents released by the U.S. State Department.

DAVID CORREIA

Correia, another Florida businessman, pleaded guilty last year to making false statements to the Federal Election Commission, and duping investors in Fraud Guarantee, a company he founded with Parnas that paid Giuliani $500,000.

VICTORIA TOENSING AND JOE DIGENOVA

Toensing and diGenova are married Washington lawyers who helped Giuliani represent Trump in his post-election lawsuits.

They represented Ukrainian oligarch Dmytro Firtash, who is fighting extradition from Vienna on U.S. bribery and racketeering charges. FBI agents raided the couple's home earlier this week and seized a cellphone used by Toensing.

JOHN SOLOMON

Solomon worked for The Hill, a Washington newspaper and website covering Congress, when he wrote a series of pieces that Yovanovitch testified to Congress were part of a smear campaign against her that Giuliani appeared to be behind. The Hill later said Solomon failed to identify important details about key Ukrainian sources, including the fact that they had been indicted or were under investigation.

-Reuters

'At that point, he [Giuliani] will need to adopt a defense strategy that may put him at odds with his former client,' he said.

Mariotti continued: 'When a lawyer, particularly a famous former federal prosecutor like Giuliani, faces time in prison, the incentive to reduce that sentence is significant.'

'Just like Michael Cohen, Giuliani will have every incentive to help federal prosecutors if it could potentially reduce his prison sentence,' he wrote. 'That could make the Giuliani prosecution far more consequential than it appears at first glance, given his role in everything from the defense of Trump's impeachment to the Jan. 6 insurrection.'

'Without Trump's protection or financial support, Giuliani's loyalty would seem to have a limited shelf life.'

The claims from Mariotti come after the FBI carried out a raid on Giulani's home last week – seizing at least 10 cell phones and computers.

Giuliani, who is the former U.S. Attorney for the Southern District of New York and former mayor of New York City, has slammed the 6:00 a.m. raid as 'illegal' and 'unconstitutional'.

He has sought to discredit the federal investigation, saying the raid by seven FBI agents was unnecessary because he offered for two years to provide prosecutors his electronic devices and to 'talk it over with them'.

'They won't explain to me what they're looking into for two years,' Giuliani told Fox News' Tucker Carlson.

Giuliani's lawyer, Robert Costello, has previously said proposed meetings between investigators and Giuliani's legal team didn't take place because prosecutors wouldn't agree to a precondition that they first disclose more about the probe.

According to the warrant, investigators are seeking to review Giuliani's phones and computers for communications with more than a dozen people, including a high-ranking prosecutor in Ukraine.

They also are searching for communications with any U.S. government official or employee relating to Marie Yovanovitch, the US ambassador to Ukraine who was ousted by the Trump administration in 2019, the warrant said.

Giuliani was spotted out with his alleged girlfriend in New York City just days after the raid.

The 76-year-old stepped out on Saturday in Manhattan with Maria Ryan - his rumored 56-year-old girlfriend and former alleged mistress.

Giuliani, who was wearing a face mask, was seen arriving at a cafe close to his apartment on the Upper East Side where he was met by Ryan.

The pair arrived in separate cars but left the cafe together. Giuliani appeared to be accompanied by an unidentified younger woman as he left the cafe.

Ryan, who is believed to have three children, was spotted behind the wheel of the car as they left.

Giuliani could be seen going through what appeared to files while sitting in the front seat.

Ryan, who stepped down as CEO of a New Hampshire hospital in December, has reportedly been dating Trump's personal lawyer since 2018.

Giuliani has previously denied allegations he had an affair with Ryan while he was still married to his third wife Judy Giuliani.

Ryan was named as Giuliani's alleged mistress in court documents filed back in 2018 amid his divorce from Judy.

Giuliani denied there was any proof of an affair despite being spotted spending the night together at an upstate New York hotel.

The pair were pictured attending a White House dinner hosted by President Trump in 2019.

Giuliani referred to Ryan as an 'associate' earlier this year when he admitted to billing Trump $20,000 per day to dispute the election results - despite previously denying demanding money for his legal services.

He told the New York Times in January that his associate - who he named as Maria Ryan - had sent an email to at least three Trump campaign officials in November demanding payment.

Their sighting together came just days after the FBI executed a search warrant on his Manhattan home as part of an investigation into his dealings in Ukraine.

Agents seized more than 10 cell phones and computers from Giuliani's Manhattan apartment and office in raids.

The federal probe is examining Giuliani's interactions with Ukrainian figures and whether he violated a federal law that governs lobbying on behalf of foreign countries or entities.

Giuliani has insisted that all of his activities in Ukraine were conducted on behalf of former President Donald Trump.

At the time, Giuliani was leading a campaign to press Ukraine for an investigation into now-President Joe Biden and his son Hunter.

It has since emerged that Trump's allies are deeply troubled by the Giuliani raid.

Their fears emerged as a transcript of a conversation between Giuliani and a Ukrainian official was published, laying bare what seems to be the substance of the FBI's investigation.

A transcript of his July 2019 call, which took place between Giuliani and Andriy Yermak, who at the time was newly-elected President Volodymyr Zelensky's top foreign policy advisor, was published by BuzzFeed on Friday.

Giuliani attempts, on the call, to establish a working relationship between Kiev and Washington DC - bypassing the usual State Department channels to speak directly for Trump, although he is at pains to emphasize that he cannot speak for his boss.

He is particularly emphatic that the new president should investigate Biden, who, while serving as vice president, had pushed for the firing of the country's chief prosecutor, Viktor Shokin.

Shokin, who was seen with suspicion in the West, was fired in March 2016, as part of an anti-corruption initiative developed by the State Department and coordinated with the European Union and the International Monetary Fund.

Giuliani seeks an investigation, and wants Zelensky to publicly accuse Biden.

He also wants Ukraine to investigate possible interference in the election, and back the idea that Ukraine - not Russia - could have tried to tip the scales in favor of Trump.

'All we need from the president is to say: I'm gonna put an honest prosecutor in charge, he's gonna investigate and dig up the evidence, that presently exists and is there any other evidence about involvement of the 2016 election,' Giuliani tells Yermak.

'And then the Biden thing has to be run out.'

Giuliani says: 'He offered Poroshenko a $1.2 billion loan guarantee, critical to Poroshenko's success as president, in exchange for getting rid of a prosecutor general, that he didn't wanna get rid of.

'Somebody in Ukraine's gotta take that seriously.'

Giuliani then turns to Hunter Biden's energy firm, Burisma.

As part of a campaign to discredit Joe Biden and accuse him of influence peddling, Giuliani was keen for details of Hunter's work on the board of the company.

'That investigation of Burisma has been started, discontinued, started and discontinued about three times,' Giuliani complained.

He also issued a bizarre warning to the new president, via his aide, saying: 'What I wanted to tell the president is: be careful.

'Probably it's a little arrogant to say that. I shouldn't say that about being careful.

'But just as a person interested: be careful of the people around you, because… they can very easily… they can very easily get you into trouble.'

He did not provide more detail.