President Donald Trump reiterated his strong support for NATO and pressed German Chancellor Angela Merkel to meet NATO's military spending target, in the first face-to-face meeting between the two leaders.
They shook hands and smiled for the cameras before entering the West Wing.
The Oval Office meeting had been scheduled for Tuesday, before a major snowstorm in the eastern United States forced a postponement.
Both leaders described their meeting in brief remarks to reporters as having been very good. Mr Trump said they both discussed many things.
In a press briefing later, Mr Trump said he and the Chancellor agreed on the need for a peaceful solution into the conflict in Ukraine.
Yesterday, the United States reiterated its condemnation of Russia's annexation of Crimea, vowing to maintain related sanctions until Moscow returns the strategic Black Sea peninsula to Kiev.
Mr Trump also said he backed the NATO alliance but stressed that some member states were not contributing enough.
"I reiterated to Chancellor Merkel my strong support for NATO as well as the need for our NATO allies to pay their fair share for the cost of defence," he said.
"Many nations owe vast sums of money from past years and it is very unfair to the United States. These nations must pay what they owe".
Ms Merkel said she told Mr Trump Germany needs to meet NATO spending goals. The two also discussed Afghanistan.
Mr Trump said he expected the United States to do "fantastically well" in trade with Germany, while Ms Merkel said she hoped the United States and the European Union could resume discussions on a trade agreement.
The President said he did not believe in isolationism but that trade policy should be fairer.
"We held a conversation where we were trying to address also those areas where we disagree, but we tried to bring people together ... (and) tried to find a compromise that is good for both sides," Ms Merkel said.
Mr Trump said he "very seldom" regrets anything he tweets, brushing off questions about his claims without evidence tha this predecessor Barack Obama wiretapped him during last year's presidential campaign.
He said, "At least we have something in common," apparently referring to reports during Mr Obama's presidency that the United States bugged Ms Merkel's phone.
Congressional leaders from both political parties say they do not believe Mr Trump was wire tapped.
The meeting is consequential for both sides.
As a presidential candidate, Mr Trump criticised Ms Merkel for allowing hundreds of thousands of refugees into Germany.
At the news conference, she hinted at differences, saying: "This is obviously something we had an exchange of views about."
Relationship building is a less overt but important agenda item. Ms Merkel had close relations with Trump's Democratic and Republican predecessors, Mr Obama and George W Bush, and she is likely to seek a strong working relationship with Mr Trump despite major policy differences and wariness in Germany about him.
"Those who know the chancellor know that she has a knack for winning over people in personal discussions. I am sure that Donald Trump will not be immune," said Juergen Hardt, a conservative MP who helps coordinate transatlantic relations for the German government.
