US President Donald Trump is "extremely confident" that the Justice Department will produce evidence backing up his claim that predecessor Barack Obama wiretapped his New York skyscraper during the election.
White House spokesman Sean Spicer said the president believes that information yet to be released will "vindicate him".
The comments came a day after the Justice Department asked lawmakers for more time to produce that evidence.
The House intelligence committee gave the department until March 20, the first day of its hearings on Russia's interference in the 2016 election and possible contacts between Trump advisers and Russians.
Mr Trump made the wiretapping allegation earlier this month, strongly denied by Mr Obama.
A spokesman for the committee's Republican chairman said if the justice department does not meet the new deadline, the panel might use its subpoena power to gather information.
"If the committee does not receive a response by then, the committee will ask for this information during the March 20 hearing and may resort to a compulsory process if our questions continue to go unanswered," said Jack Langer, a spokesman for Representative Devin Nunes.
In its response, the justice department said it needed extra time to "review the request in compliance with the governing legal authorities and to determine what if any responsive documents may exist".
Mr Trump's assertions have put his administration in a bind.
Current and former administration officials have been unable to provide any evidence of Mr Obama wiretapping Trump Tower, yet the president's aides have been reluctant to publicly contradict their boss.
Mr Trump himself has not commented on the matter since his March 4 tweets.
The president's accusations came amid numerous political questions surrounding his associates' possible ties to Russia.
The FBI is investigating Trump associates' contacts with Russia during the election, as are House and Senate intelligence committees.
The White House has asked those committees to also investigate Mr Trump's unverified wiretapping allegations against Mr Obama.