US President Donald Trump will not invoke executive privilege to block former FBI Director James Comey's scheduled testimony before Congress this week, the White House said on Monday.

"In order to facilitate a swift and thorough examination of the facts sought by the Senate Intelligence Committee, President Trump will not assert executive privilege regarding James Comey's scheduled testimony," White House spokeswoman Sarah Sanders told reporters.

Mr Comey was leading a Federal Bureau of Investigation probe into alleged Russian meddling in last year's US presidential election and possible collusion by Mr Trump's campaign when the president fired him last month.