Former CIA director John Brennan says he had noticed contacts between associates of Donald Trump's presidential campaign and Russia during the 2016 election and grew concerned Moscow had sought to lure Americans down "a treasonous path".
Brennan, who headed the agency until Trump became president in January, also told a congressional hearing he personally warned the head of Russia's FSB security service in a phone call last August that meddling in the election would hurt relations with the US.
Separately, the top US intelligence official, Dan Coats, sidestepped a question on a Washington Post report that Trump had asked him and the National Security Agency chief to help him knock down the notion there was evidence of such collusion.
However, Coats did say he made clear to Trump's administration that "any political shaping" of intelligence would be inappropriate.
The comments by Brennan and Coats, the Director of National Intelligence, added fuel to a controversy that has engulfed Trump since he fired FBI director James Comey two weeks ago amid the agency's investigation into possible collusion between people associated with his presidential campaign and Russia.
"I encountered and am aware of information and intelligence that revealed contacts and interactions between Russian officials and US persons involved in the Trump campaign," Brennan said in testimony to the House of Representatives intelligence committee.
He said he could not say definitively there was actual collusion.
Brennan's testimony was the first public confirmation of the worry at high levels of the US government last year over suspicious contacts between Trump campaign associates and Moscow.
It was also the most complete account to date of the CIA's thinking at a time when intelligence agencies were putting together evidence that Russia was interfering in the heated presidential race to help Trump, a Republican, defeat Democratic Party candidate Hillary Clinton.
In response to the hearings, the White House said there was still no evidence of collusion between Trump's team and Moscow.
