Key members of Congress say they will honor President Donald Trump's request to investigate his unsubstantiated claim that Barack Obama overstepped his authority as president and had Trump's telephones tapped during the election campaign.

A U.S. official said the FBI has asked the Justice Department to dispute Trump's allegation, though no such statement has been issued.

Obama's intelligence director also said no such action was taken.

Trump made his startling claim of presidential abuse of power in a series of tweets early Saturday. They capped a week in which the positive reaction to his address to Congress quickly evaporated amid the swirl of allegations and revelations about contacts between Trump aides and a Russian official, both during and after the presidential election that Russia is believed to have meddled in.