Felix Sater - an associate of President Donald Trump who played a key role in the probe into Russian election interference - traveled the world and gathered intelligence for years to help the US government 'combat terrorists and rogue states,' a newly unsealed court document reveals.

The document, written by federal prosecutors a decade ago and released today by a federal judge, confirms the 53-year-old's seemingly fantastical claim that he was building 'Trump Towers by day and hunting bin Laden by night'.

Prosecutors described what they called Sater's 'extraordinary cooperation' as a covert asset in collecting information on Russia, Al-Qaeda, the Taliban, North Korea, as well as on the Italian mafia in the US in the late 1990s and 2000s.

Felix Sater, a former business associate of President Trump, supplied information on the Taliban, Al-Qaeda, and American mobsters to the US government, a newly released court document shows

The letter was filed by prosecutors in 2009 requesting a lenient sentence for him after he pleaded guilty to racketeering in a stock fraud case in 1998

The letter details that Sater 'passed on specific information about Osama Bin Laden, including what were believed to be Bin Laden's satellite telephone numbers'

The intelligence he gathered included the purported satellite phone numbers for Osama bin Laden and his whereabouts after the September 11, 2001 attacks, details on an assassination plot against then-President George W. Bush and 'information on North Korean nuclear capabilities,' the document says.

A Soviet-born emigre who befriended Trump in the 2000s, Sater served jail time for slashing a man with a broken cocktail glass in 1991.

He began cooperating with the US government in 1998 after pleading guilty to racketeering in a $40 million stock-fraud case involving New York mafia figures.

The partially redacted government document, referred to as a 5K1 letter in legal terms, was filed by prosecutors in 2009 requesting a lenient sentence for Sater due to his work with the CIA and FBI targeting the mafia and Al-Qaeda.

He dodged jail time with a $25,000 fine.

The 10-page letter describes him as an 'exemplary cooperator who worked diligently to further the aims of the missions to which he was assigned.'

The letter was released on Friday by US District Court Judge Leo Glasser in response to a lawsuit by The Intercept, an online news organization, to reveal more information about Sater's dealings with the US government

Sater (seen in 2005) was a prominent figure in the Trump-Russia probe because he pursued a business deal to build a Trump tower in Moscow during the 2016 presidential campaign

It said he played a key role in weakening the Mafia's presence on Wall Street, as well as helping the US government dismantle money laundering operations in Russia, Cyprus, Turkey, and elsewhere.

'For approximately ten years, Sater continuously worked with prosecutors and law enforcement agents to provide information crucial to the conviction of over twenty different individuals, including those responsible for committing massive financial fraud, members of La Cosa Nostra organized crime families and international cyber-criminals,' wrote a former assistant US attorney.

'Additionally, Sater provided the United States intelligence community with highly sensitive information in an effort to help the government combat terrorists and rogue states.'

The letter was released on Friday by US District Court Judge Leo Glasser in response to a lawsuit by The Intercept, an online news organization, and others to reveal more information about Sater's dealings with the US government.

His international exploits were documented by BuzzFeed News in 2018, but Sater told ABC News he feels vindicated by the newly-released government account.

'Most people don't believe the things I've done, but I've done them. So with this happening, the way it's being confirmed by the Justice Department and federal courts, gives me honestly some satisfaction,' Sater said.

He also told BuzzFeed: 'Given the events of the last three years, I'm happy that people can now judge me for the bad that I've done and the good that I've done. I just hope that 20 years of service to protect America adds a little to the plus column.'

The letter only documents Sater's actions in the 1990s and 2000s, but he told ABC News he continued to provide the US government with information until Special Counsel Robert Mueller began his investigation into Trump's ties to Russia.

Sater worked with Trump (seen in 2007) on a hotel condominium project in Manhattan's SoHo neighborhood and tried to work out a deal for a Trump branded property in Russia

Sater was a high-profile figure in the probe because of his role in helping Trump's former lawyer Michael Cohen negotiate a deal to build a Trump Tower in Moscow during the 2016 presidential campaign.

The Russian-American businessman and property developer told Cohen in a leaked email that Russian President Vladimir Putin could help Trump win the election if the deal went through.

He was mentioned more than 100 times in Mueller's final report.

The skyscraper deal was later abandoned, and Cohen was sentenced to three years in federal prison after pleading guilty to tax evasion, campaign-finance violations and lying to Congress about the project.

He told ABC that in his career as a covert asset, he was never asked for and never provided information on Trump.

Sater defended his actions by claiming to be a patriot who worked closely with American spies at great personal risk.

'I love this country more than anything else,' Sater told The Associated Press, adding he was not moved to cooperate by the possibility of a jail sentence.

The letter also documents Sater's crimes, including when, in his mid-twenties, he swindled investors out of $40 million and then 'carefully laundered' it through offshore accounts with the help of mafia figures.

Police seized loaded guns and documents detailing the stock fraud as well as Sater's role in it in January 1998.

Sater was overseas, and upon learning of the seizure, offered US intelligence officers information about Afghanistan's Northern Alliance, which was fighting the Taliban.

'During the spring and summer of 1998, Sater traveled to Central Asia where he gathered and passed on information to United States sources about the Northern Alliance's desire to resell Stinger missiles to the United States government as well as information about the Taliban and Osama bin Laden, among other things,' the letter states.

'Sater contacted the FBI during this period and kept agents apprised of his activities overseas.'

The letter also said Sater provided 'specific, detailed information to the Central Intelligence Agency ('CIA'), FBI and other agencies' in 1998, which included 'what were believed to be bin Laden's satellite telephone numbers and information about who was supplying arms to bin Laden.'

He continued to collect information on bin Laden after the 9/11 attacks, working with a precious stone dealer who had who had Taliban contacts.

'Sater went above and beyond what is expected of most cooperators and placed himself in great jeopardy in so doing,' the letter said.