Media playback is unsupported on your device Media caption Who is Rudy Giuliani?

Rudy Giuliani, President Donald Trump's personal lawyer, used an Oval Office meeting to seek the release of a jailed client, US media report.

The request reportedly prompted a swift rebuke from then-Secretary of State Rex Tillerson, who said it would constitute interference in an open investigation.

Mr Giuliani reportedly asked Mr Tillerson in 2017 to help free his client, an Iranian-Turkish gold trader.

Mr Trump had encouraged Mr Tillerson to work with Mr Giuliani, US media said.

The trader represented by Mr Giuliani, Reza Zarrab, eventually pleaded guilty in New York to orchestrating a conspiracy to launder billions of dollars in gold and cash to Iran in order to evade US sanctions.

The defendant's lawyers - Mr Giuliani and former US Attorney General Michael Mukasey - reportedly proposed dropping the case against their client in exchange for an American pastor held in Turkish custody.

Mr Giuliani confirmed to US media he had sought a prisoner swap.

According to Bloomberg News, which first reported the Oval Office meeting, Mr Trump reportedly pressed Mr Tillerson to help prod the US Department of Justice into dropping charges against Mr Giuliani's client.

Image copyright The Washington Post/Getty Images Image caption Mr Tillerson listens as President Donald Trump speaks during a 2017 cabinet meeting

"The president says, 'Guys, give Rex your pitch,'" a source told the Washington Post.

US media said other aides present at the meeting joined Mr Tillerson in pointing out to the president that it would be inappropriate to interfere in a criminal investigation.

After the meeting, Mr Tillerson emphasised to then-Chief of Staff John Kelly that such a move would be illegal.

Mr Tillerson was fired by the president in March 2018.

Turkish President Recep Tayyip Erdogan had also personally lobbied for the trader's release, according to US media.

Media playback is unsupported on your device Media caption Mr Giuliani is alleged to have sought to dig up dirt on Democrat candidate Joe Biden

In late 2017, after the attempted prisoner swap failed, Zarrab pleaded guilty.

He testified in court that the money-laundering scheme, which involved a state-owned Turkish bank, had been approved by Mr Erdogan. Turkish officials have denied wrongdoing.

Mr Giuliani is already facing intense scrutiny for his work at the White House, and his role as Mr Trump's personal lawyer.

The former US attorney for New York is being investigated by his old office following the arrest of two of his associates for alleged violation of campaign finance laws, Bloomberg reported.

The pair, both Trump donors, have peddled unsubstantiated corruption claims against top Democratic presidential contender Joe Biden.

Lev Parnas and Igor Fruman are also under scrutiny in a congressional impeachment investigation into whether Mr Trump improperly pressured Ukraine to investigate the Bidens.

Asked on Thursday if he knew Mr Parnas and Mr Fruman, Mr Trump disavowed them.

"I don't know those gentleman," Mr Trump said. "Maybe they were clients of Rudy, you'd have to ask Rudy."

The two Soviet-born businessmen dined with the president at the White House in May last year, according to the Wall Street Journal.