U.S. President Donald Trump said on Thursday he did not make and does not possess any tapes of his conversations with James Comey, after suggesting last month he might have recordings that could damage the former FBI director.

"With all of the recently reported electronic surveillance, intercepts, unmasking and illegal leaking of information, I have no idea whether there are 'tapes' or recordings of my conversations with James Comey, but I did not make, and do not have, any such recordings," Trump wrote on Twitter.

Lawmakers investigating allegations of Russian meddling in the U.S. 2016 election had asked the White House for any such recordings of Comey, whom Trump fired on May 9.

Shortly after dismissing Comey, Trump mentioned the possibility of tapes in a Twitter post.

"James Comey better hope that there are no 'tapes' of our conversations before he starts leaking to the press!" Trump wrote on Twitter on May 12.

Allegations of ties to Russia have cast a shadow over Trump's first five months in office, distracting from attempts by his fellow Republicans in Congress to overhaul the U.S. healthcare and tax systems.

Comey's firing sparked a political firestorm. The former FBI head testified before a Senate committee that Trump had asked him to drop a probe into former national security adviser Michael Flynn's alleged ties to Russia.

Trump has privately told aides that the threat of the existence of tapes forced Comey to tell the truth in his recent testimony, a source familiar with the situation said. The White House had said Trump would likely clarify whether he had tapes of Comey by the end of this week.

Adam Schiff, the top Democrat on the House of Representatives Intelligence Committee, said Trump still had questions to answer about possible tapes.

"If the President had no tapes, why did he suggest otherwise? Did he seek to mislead the public? Was he trying to intimidate or silence James Comey? And if so, did he take other steps to discourage potential witnesses from speaking out?" Schiff said in a statement.

Earlier on Thursday, CNN reported that two top U.S. intelligence officials told investigators Trump suggested they publicly deny any collusion between his campaign and Russia, but they did not feel he had ordered them to do so.

Director of National Intelligence Dan Coats and National Security Agency Director Admiral Mike Rogers met separately last week with investigators for Special Counsel Robert Mueller and the Senate Intelligence Committee, according to CNN.

The two officials said they were surprised at Trump's suggestion and found their interactions with him odd and uncomfortable, but they did not act on the president's requests, CNN reported, citing sources familiar with their accounts.

The Kremlin has denied U.S. intelligence agencies' conclusion that Moscow tried to tilt the election campaign in Trump's favour, using such means as hacking into the emails of senior Democrats.

Trump has denied any collusion, and he continued to cast doubt on the investigations in a series of tweets on Thursday morning.