The White House is in a downward spiral, a Republican senator claimed on Monday, as Donald Trump's administration was plunged into fresh turmoil by a report claiming the president revealed classified information to Russia's top diplomat.

With the White House still battling the political fallout from the firing of FBI Director James Comey last week, the president faced fresh controversy for allegedly revealing to Sergey Lavrov and Sergei Kislyak, the Russian ambassador, closely held intelligence from a US intelligence ally about an Islamic State plot during an Oval Office meeting last week.

"The White House has got to do something soon to bring itself under control and in order," Republican Senator Bob Corker, who is chairman of the Foreign Relations Committee, told reporters at the Capitol.

"Obviously they're in a downward spiral right now and they've got to figure out a way to come to grips with all that's happening."