One of America's top spies has shot down US President Donald Trump's suggestion British intelligence wiretapped Trump Tower on behalf of former president Barack Obama, describing such an order as a breach of the Five Eyes alliance between the US, UK, Australia, New Zealand and Canada.
National Security Agency head Admiral Michael Rogers and FBI director James Comey were grilled by a congressional committee in Washington DC on Monday about Russian interference in the 2016 US presidential campaign.
The committee also scrutinised Australian Julian Assange's WikiLeaks' alleged collaboration with Russia in releasing emails hacked from Democrat Party presidential candidate Hillary Clinton's campaign director John Podesta's account.
"No sir. Nor would I," Rogers, asked if he requested British intelligence counterparts to wiretap Trump on behalf of Obama, told the House Intelligence Committee.
"That would be expressly against the construct of the Five Eyes agreement that has been in place for decades."
Comey testified there was "no information" supporting Trump's claims Obama ordered surveillance of Trump Tower during the election campaign.
Rogers said he agreed with the British response that the wiretapping claim was "nonsense and utterly ridiculous" and it "clearly frustrates a key ally of ours".
"My view is the same as director Comey," Rogers said.
"I have seen nothing on the NSA side that we engaged in any such activity nor that anyone ever asked us to engage in such activity."
Comey testified Russian intelligence officials used an intermediary to pass Podesta's hacked emails to WikiLeaks before the election.
"We assessed they used some kind of cut out," Comey said.
"They didn't deal directly with WikiLeaks."
Jim Himes, a Democrat on the Intelligence Committee, queried why Trump "will attack anyone and everyone" including allies like Australia but would not criticise Russia or Russian President Vladimir Putin.
"He will attack the cast of Hamilton," Himes told Comey.
"He will attack (Democrat senator) Chuck Schumer.
"He will attack our allies Mexico, Australia, Germany.
"He will attack the intelligence community which you lead associating you with McCarthyism and Nazism, but there is one person and one country which is immune, which is inoculated from any form of presidential attack no matter what the behaviour."
Trump tweeted during the hearing, which was broadcast live on US cable TV news channels.
"The NSA and FBI tell Congress that Russia did not influence electoral process," Trump wrote.
In another tweet he wrote: "FBI Director Comey refuses to deny he briefed President Obama on calls made by (former national security adviser) Michael Flynn to Russia".