Former US President Barack Obama warned then-President-elect Donald Trump not to give the post of national security adviser in his administration to Michael Flynn who was eventually fired in a controversy about ties to Russia, a former Obama aide says.
Mr Obama gave the warning in an Oval Office meeting with Mr Trump just days after the Republican's surprise election win last November 8.
White House spokesman Sean Spicer, responding to the reports, told a news briefing on Monday: "It's true that the president, President Obama, made it known that he wasn't exactly a fan of General Flynn's" during a one-hour meeting with Mr Trump after the election.
An Obama spokesman initially declined to comment.
Mr Flynn has emerged as a central figure in probes into allegations of Russian meddling in the 2016 US election and possible collusion between Mr Trump's campaign and Moscow.
He had been pushed out by Mr Obama in 2014 from his job as director of the Defense Intelligence Agency, or DIA, during the Democratic president's term in office.
A former US deputy attorney general, Sally Yates, is expected to tell a Senate Judiciary subcommittee later on Monday that she had warned the White House counsel after Mr Trump took office that Flynn had not told the truth about conversations he had held with Russia's ambassador to Washington.
Mr Trump fired Flynn, a retired general, in February for failing to disclose talks with Ambassador Sergei Kislyak about US sanctions on Moscow and then misleading Vice President Mike Pence about the conversations.
Congressional committees began investigating after US intelligence agencies concluded that Russian President Vladimir Putin had ordered hacking of Democratic political groups to try to sway the election toward Mr Trump. Moscow has denied any such meddling.
Mr Trump has also dismissed the allegations, suggesting instead that Mr Obama might have wiretapped Trump Tower in New York or that China may have been behind the cyber-attacks.
He has provided no evidence and neither scenario has been supported by intelligence agencies.
Hours before Monday's Senate hearing, Mr Trump insinuated that Ms Yates, an Obama administration appointment, had leaked information on Mr Flynn to the media.
"Ask Sally Yates, under oath, if she knows how classified information got into the newspapers soon after she explained it to W.H. Council," Mr Trump wrote on Twitter, apparently mis-spelling the word counsel.
In another Twitter post, Mr Trump noted Mr Flynn had been granted top security clearance while working in the Obama administration.
Mr Flynn was fired from the DIA in 2014 for what officials familiar with the issue said was a disruptive management style that included instructing analysts to find intelligence substantiating improbable theories that some subordinates came to call "Flynn facts".