Donald Trump faces further difficulty after leading Republicans refused to back up his claims of wire-tapping by Barack Obama.
Senate majority leader Mitch McConnell and Devin Nunes, chair of the House intelligence committee, say there is no evidence to support Mr Trump's claim - a stance which is likely to fuel speculation that Mr Trump enjoys little confidence within his own party.
The unsubstantiated allegations, which the President made on Twitter over the weekend, have rocked the American political arena. In the wake of the tweets, denials were roundly issued by former members of the Obama administration.
Obama himself has mocked Mr Trump in response to the allegations, while James Comey, the FBI Director, also reportedly asked the Justice Department to deny the claims.
However White House press secretary Sean Spicer made it clear Mr Trump would not withdraw the allegation until it was thoroughly dismissed.
He asked reporters: "Why would he withdraw the claim until it is adjudicated?"
"He's not walking back or regretting anything."