Donald Trump's first meeting with Angela Merkel produced an awkward moment as the US president did not shake the German leader's hand in front of photographers in the Oval Office.
Mr Trump told photographers to "send a good picture back to Germany, please".
He said the leaders had enjoyed "very good" talks while Mrs Merkel praised the "friendly reception".
Photographers then shouted "handshake!" and Mrs Merkel quietly asked Mr Trump "do you want to have a handshake?"
There was no response from the president, who looked ahead with his hands clasped.
German weekly Der Spiegel commented that "the overall impression of this meeting was rather cool".
German daily Bild wrote on its website: "Trump didn't want to give Merkel his hand in his office!"
At a joint news conference with the German chancellor, Mr Trump hit back at claims his "America First" agenda is isolationist.
He said: "I don't believe in an isolationist policy."
Mr Trump has been deeply critical of foreign trade and national security agreements. Yet the president suggested that he is only trying to revise them to better serve US interests, rather than pull back from the world entirely.
Mr Trump said trade agreements have led to greater trade deficits, although the US trade deficit with Germany was 64.9 billion dollars last year, the lowest since 2009, according to the Commerce Department.
Mr Trump bristled at the suggestion from a German reporter that his policies could be interpreted as isolationist.
He said: "I don't know what newspaper you're reading, but I guess that would be an example of fake news."
Donald Trump also stood by his unproven claim that his predecessor Barack Obama wiretapped his phones.
The US president suggested he was the victim of the same sort of surveillance the Obama administration was once alleged to have used to monitor German Chancellor Angela Merkel's calls.
"At least we have something in common, perhaps," Mr Trump said during a joint news conference with Mrs Merkel.
The chancellor, who was making her first visit to the White House since Mr Trump took office, did not weigh in on the 2013 incident, which angered many in Germany.
Mr Trump's allegations against Mr Obama have sparked reactions ranging from bafflement to anger in Washington, with both Democrats and Republican lawmakers saying they have no evidence to support his claim.
But the White House's refusal to back down has created more problems for the new administration.
On Thursday, spokesman Sean Spicer defended the president's comments by repeating a Fox News analyst's report that GCHQ, the British electronic intelligence agency, had helped Mr Obama wiretap Mr Trump.
The agency vigorously denied the charge and Britain's ambassador to Washington, Kim Darroch, complained directly to White House officials.
Mr Trump tried to distance himself from the report on Friday.
"All we did was quote a certain very talented legal mind who was the one responsible for saying that on television," Mr Trump said, referring to analyst Andrew Napolitano. "You shouldn't be talking to me, you should be talking to Fox."
The British government said the White House has promised it will not repeat the allegation. Mr Spicer, speaking with reporters following Mr Trump's news conference, said: "I don't think we regret anything."
Mr Trump tweeted earlier this month that Mr Obama "was tapping my phones in October" and compared the incident to "Nixon/Watergate" and "McCarthyism".
The claim is prompting growing bipartisan agreement that there is no evidence to back up the claim and mounting pressure to retract the statement.
The Senate Select Committee on Intelligence weighed in on Thursday, finding "no indications" that Trump Tower was the subject of surveillance.
Republicans in Congress also said Mr Trump should retract his claims. Charlie Dent called the accusation against Britain "inexplicable" and the accusation against Mr Obama unfounded.
"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," Mr Dent said.
Donald Trump’s claim that has he was wiretapped by Barack Obama is under increasing assault after a congressional committee said it had seen no evidence to support the allegation and it did not believe that it happened.