Top White House aide Kellyanne Conway said she had no evidence to back up Donald Trump's claim that his predecessor had wiretapped him, after suggesting her boss may have been spied upon using other methods.
The Trump administration is under mounting pressure to provide proof to shore up the president's unsubstantiated allegation that Barack Obama ordered the phones to be tapped at Trump Tower during the election campaign.
"The answer is I don't have any evidence and I'm very happy that the House Intelligence Committee are investigating," Conway told ABC television.
The senior aide to the president was being pressed to explain weekend comments that seemed to suggest the Obama administration ordered wide-scale surveillance of her boss.
"What I can say is there are many ways to surveil each other," Conway told New Jersey's Bergen County Record in a wide-ranging interview published Sunday.
"You can surveil someone through their phones, certainly through their television sets -- any number of ways," including "microwaves that turn into cameras," she told the paper. "We know this is a fact of modern life."
Conway backed away on Monday from the comments -- which were greeted with online ridicule -- telling ABC's "Good Morning America" she had been referring to "surveillance generally" and not to the president's allegations regarding Trump Tower.
Trump, meanwhile, appeared to take the media to task over its skeptical treatment of Conway.
"It is amazing how rude much of the media is to my very hard working representatives," he tweeted minutes after she wrapped up appearances on several morning talk shows. "Be nice," he said, "you will do much better!"
Both Obama, through a spokesman, and his director of national intelligence James Clapper have denied ordering any wiretapping operation targeted at Trump.
But Trump's White House is standing by its demand for a congressional investigation into the allegations.
The House Intelligence Committee's Republican chairman Devin Nunes and top ranking Democrat Adam Schiff had written to the Justice Department asking for evidence to be provided by Monday in support of Trump's allegation.
The DOJ instead asked for "additional time to review the request in compliance with the governing legal authorities and to determine what if any responsive documents may exist," spokeswoman Sarah Isgur Flores said Monday.
Schiff said Sunday he doubted any evidence would be forthcoming, and that he would press the demand again during a wide-ranging open hearing set for March 20 on the issue of Russian meddling in the election.
After the DOJ asked for more time on Monday, Schiff tweeted, "We are urging that they do so promptly but no later than our hearing on March 20."
Top Republican lawmaker and frequent Trump critic Senator John McCain on Sunday challenged Trump to prove the wiretapping claim -- or else retract it.