At a joint news conference following the leaders' sit-down meeting (and handshake snafu), a German reporter asked Trump about his administration's recent spat with another major US ally.
The German Chancellor's White House meeting kicked off with an awkward photo shoot with President Trump, as he refused to shake her hand.
The two were left to talk, based on the premise that, in Merkel's words, "it's much better to speak with each other than past each other".
Today he expressed support for North Atlantic Treaty Organisation but pushed for nations to "pay what they owe" - working toward contributing at least 2 percent of each member country's GDP. Trump still says he was witetapped by Obama.
Mr Merkel said she hoped the United States and the European Union could resume discussions on a trade agreement and that she had told Mr Trump Germany needed to meet North Atlantic Treaty Organisation spending goals.
Her visit was scheduled for Tuesday but had to be postponed due to a snowstorm.
Immediately after the news conference, White House Press Secretary Sean Spicer told reporters, "I don't think we regret anything".
Meanwhile, the Justice Department has delivered documents to the House and Senate investigators relevant to Trump's allegations that Obama wiretapped him.
"It's the initials for the British intelligence spying agency". He repeated those claims with Ms. Merkel by his side.
Their agenda in White House meetings included discussions on strengthening North Atlantic Treaty Organisation, fighting the Islamic State group, the conflict in Afghanistan and resolving Ukraine's conflict, all matters that require close cooperation between the USA and Germany.
The British government said the White House has promised it won't repeat the allegation. "That's not the same as saying it was rubbish in the first place", he said.
The health care overhaul would kill much of Obama's 2010 health care law and create new tax credits and curbs on Medicaid, the federal-state health care program for lower-income people. Both leaders described their meeting in brief remarks to reporters as having been very good.
The world leaders are expected to discuss matters such as North Atlantic Treaty Organisation, the European Union, Russian President Vladimir Putin and trade, BBC Newsreported.
Merkel is likely to press Trump for assurances of support for a strong European Union and North Atlantic Treaty Organisation and a commitment to fight climate change.
Before coming to office in January, Trump had set the tone by calling Merkel's acceptance of refugees a "catastrophic mistake" and suggestion she was "ruining Germany".
Merkel, who takes a cautious, analytical approach to politics, was also one of the few world leaders who appeared to forge a deep connection with Obama, with whom she was something of a kindred spirit.
What they don't understand is that recent events have a tendency to prove Trump right, so it's also why Trump keeps beating them. From Merkel, there was only a look of amusement.
But Trump is also expected to seek her advice.
Promoting what he called an "America First" style of economic nationalism, Trump has often demanded that Germany and other North Atlantic Treaty Organisation countries contribute more to the military alliance and suggested that the defense alliance is "obsolete" in the face of the terrorist threat.