President Donald Trump has defiantly refused to back down from his explosive claim that Barack Obama wiretapped his phones.
But he sidestepped any blame for the White House decision to highlight an unverified report that Britain helped carry out the alleged surveillance.
In brushing off the diplomatic row with perhaps America's closest ally, Mr Trump also revived another - the Obama administration's monitoring of German Chancellor Angela Merkel's calls.
"At least we have something in common, perhaps," Mr Trump quipped during a joint news conference with Merkel.
Mrs Merkel, who was making her first visit to the White House since Mr Trump took office, looked surprised by the president's comment.
The Obama administration's spying infuriated Germany at the time and risked damaging the US relationship with one of its most important European partners.
Mr Trump's unproven recent allegations against his predecessor have left him increasingly isolated, with fellow Republican as well as Democratic politicians saying they have seen nothing from intelligence agencies to support his claim.
But Mr Trump, who rarely admits he is wrong, has been unmoved, leaving his advisers in the untenable position of defending the president without any credible evidence.
On Thursday, spokesman Sean Spicer turned to a Fox News analyst's contention that GCHQ, the British electronic intelligence agency, had helped Mr Obama wiretap Mr Trump.
Fox News anchor Shepard Smith said on Friday that the network could not independently verify the reports from Andrew Napolitano, a former judge and commentator who has met Mr Trump.
The GCHQ vigorously denied the charges in a rare public statement, saying the report was "utterly ridiculous and should be ignored".
According to a Western diplomat, Britain's ambassador to Washington, Kim Darroch, had told the White House on Tuesday that Mr Napolitano's assertions were not true.
Still, it was among several news reports Mr Spicer referenced in his briefing on Thursday as part of an angry defence of the president's claims.
Mr Darroch and other British officials complained directly to White House officials after the episode, and Prime Minister Theresa May's office said it had been assured the White House would not repeat the allegations.
Mr Spicer was very apologetic when confronted by Mr Darroch at a White House dinner on Thursday, the Western diplomat said.
But Mr Trump himself offered no public apologies and suggested there was nothing wrong with the White House repeating what it had heard.
"All we did was quote a certain very talented legal mind who was the one responsible for saying that on television," Mr Trump said during Friday's news conference.
"You shouldn't be talking to me, you should be talking to Fox."
Mr Spicer was also defiant on Friday, telling reporters: "I don't think we regret anything."
A White House official confirmed that Mr Darroch and Mrs May's national security adviser, Mark Lyall Grant, expressed concerns to both Mr Spicer and Mr Trump's national security adviser, HR McMaster.
The US and UK are members of the Five Eyes intelligence-sharing alliance, which prohibits members from spying on each other. Australia, Canada and New Zealand are the other members.
Some Republicans in Congress said Mr Trump should retract his claims, with Charlie Dent calling the accusation against Britain "inexplicable" and Mr Trump's accusation against Mr Obama unfounded.
He said: "A president only has so much political capital to expend and so much moral authority as well, and so any time your credibility takes a hit, I think in many ways it weakens the officeholder."