Trump's spokesman Sean Spicer insisted that the leaders “get on very well” but – as is often the case – his warm words from the White House podium were overshadowed by the president's intemperate tweets.
When Trump returned over the weekend from the first foreign trip of his presidency, his aides hailed the tour as a success and a sign of renewed and bolder US leadership on the world stage.
But, while Trump received a warm welcome in Saudi Arabia and Israel, he left behind a bitter taste in Europe after the NATO summit in Brussels and the G7 get-together of the world's richest powers in Sicily.
European leaders were especially dismayed by Trump's refusal to reaffirm US support for last year's Paris climate change accord and his failure to publicly endorse NATO's mutual defense pledge.
Germany was particularly discomfited, and Merkel wasted no time in warning German voters that the United States can no longer be relied upon as before.
Trump's response came in the early hours of Tuesday when he took to Twitter to once again demand that Germany renegotiate the terms of transatlantic trade and boost its defense spending.
“We have a MASSIVE trade deficit with Germany, plus they pay FAR LESS than they should on NATO & military,” Trump wrote, in his flamboyantly undiplomatic style. “Very bad for US. This will change.”
'Trump was not aggressive'
German officials have insisted that, as a member of the European Union, they cannot conduct bilateral trade talks with the United States and that they are not ready to dramatically increase military spending.