Donald Trump has accused former FBI director James Comey of "very cowardly" leaks, as Republican congressmen called on the US President to "clear up the matter once and for all".

Key points: Republicans call on Mr Trump to confirm whether he has tapes of any conversations

Republicans call on Mr Trump to confirm whether he has tapes of any conversations Mr Trump said he would "soon" but may face a subpoena if he does not but

Mr Trump said he would "soon" but may face a subpoena if he does not but Attorney-General Jeff Sessions is due to appear at a senate hearing on Tuesday

Taking to Twitter, Mr Trump questioned whether Mr Comey's leaking of information to a journalist was illegal.

"I believe the James Comey leaks will be far more prevalent than anyone ever thought possible. Totally illegal? Very 'cowardly!'" he wrote.

In his testimony to Congress last Thursday, Mr Comey laid bare on Capitol Hill months of distrust of the President, asserting that Mr Trump had fired him to interfere with the probe of Russia's ties to the Trump campaign.

Mr Comey also revealed that he had orchestrated the public release of information about his private conversations with the President in an effort to further the investigation.

Meanwhile, fellow Republicans have pressed Mr Trump to come clean about whether he has tapes of private conversations with Mr Comey and provide them to Congress if he does, or possibly face a subpoena.

It was a sign of escalating fallout from Mr Comey's testimony which drew an angry response from the President on Friday.

"I don't understand why the President just doesn't clear this matter up once and for all," said Republican senator Susan Collins, referring to the existence of any recordings.

Senator Collins, who is also a member of the Senate Intelligence Committee investigating Mr Trump's links to Russia, described Mr Comey's testimony as "candid" and "thorough" and said she would support a subpoena if needed.

"[Mr Trump] should voluntarily turn them over," she added.

But Mr Trump's aides have dodged questions about whether conversations relevant to the Russia investigation have been recorded, and so has the President.

Pressed on the issue Friday, Mr Trump said: "I'll tell you about that maybe sometime in the very near future."

Sessions to testify on Tuesday

Over the weekend, it was revealed that US Attorney-General Jeff Sessions has agreed to appear for sharp questioning by senators on the Senate Intelligence Committee on Tuesday — whether that hearing will be public or closed is not yet known.

Senators have expressed hope that Mr Sessions' testimony on Tuesday will help flesh out the truth of Mr Comey's allegations, including Mr Sessions' presence at the White House in February when Mr Trump asked to speak to Mr Comey alone.

Mr Comey alleges that Mr Trump then privately asked him to drop an investigation into former national security adviser Michael Flynn's contacts with Russia.

Mr Comey also has said Mr Sessions did not respond when he complained he did not "want to get time alone with the President again".

The US Justice Department has denied that, saying Mr Sessions stressed to Mr Comey the need to be careful about following appropriate policies.

"We want to be able to get his side of it," Republican senator James Lankford said.

Sorry, this video has expired Former FBI boss James Comey faced a Senate intelligence committee. (Photo: Reuters/Jonathan Ernst)

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