President Donald Trump dismissed as "fake news" allegations that Russia offered bounties for killing US troops in Afghanistan.
He said news stories about the allegations were made up to "damage me and the Republican Party".
Politicians have been demanding answers over the allegations, and Democrats have accused Mr Trump of bowing to Russian President Vladimir Putin at the risk of US soldiers' lives.
Mr Trump tweeted on Wednesday that he had not been briefed on intelligence assessments that Russia offered bounties because there was not corroborating evidence.
The Russia Bounty story is just another made up by Fake News tale that is told only to damage me and the Republican Party. The secret source probably does not even exist, just like the story itself. If the discredited @nytimes has a source, reveal it. Just another HOAX!
— Donald J. Trump (@realDonaldTrump) July 1, 2020
Those intelligence assessments were first reported by The New York Times, then confirmed by US intelligence officials and others with knowledge of the matter.
"The Russia Bounty story is just another made up by Fake News tale that is told only to damage me and the Republican Party," Mr Trump tweeted.
"The secret source probably does not even exist, just like the story itself."
The president's national security adviser, Robert O'Brien, said the intelligence was not brought to the president's attention initially because it was unverified and there was no consensus among the intelligence community.
Mr O'Brien insisted that the CIA and Pentagon did pursue the lead and briefed international allies.
But he echoed the recent White House talking point faulting not Russia but government leakers and the media for making the matter public.
He told Fox & Friends that he had prepared a list of retaliatory options for Trump if the intelligence was corroborated.
"We had options ready to go," said Mr O'Brien.
"It may be impossible to get to the bottom of it."
Mr Trump has been under pressure from politicians on Capitol Hill to address the reports.
Majority Leader Steny Hoyer and a small group of other House Democrats met with White House officials as Mr Trump downplayed the allegations.
The Democrats questioned why Mr Trump would not have been briefed sooner and pushed White House officials to have the president make a strong statement about the matter.
House Intelligence Committee Chairman Adam Schiff, one of the Democrats who attended the briefing, said it was "inexplicable" why Mr Trump will not say publicly that he is working to get to the bottom of the issue and why he will not criticise Mr Putin.
He said Mr Trump's defence that he had not been briefed was inexcusable.
"Many of us do not understand his affinity for that autocratic ruler who means our nation ill," Mr Schiff said.
Representative Mikie Sherrill, a Democrat freshman and former Navy helicopter pilot and Russia policy officer, said White House chief of staff Mark Meadows briefed the group.
She said the Democrats told the White House briefers that the president should make a statement.
"These are very concerning allegations and if they're true, Russia is going to face repercussions," Ms Sherrill said.
"We really pushed that strongly in the meeting."