And as the Washington Post noted last month, Trump has a habit of aggressively yanking the hand - and person - he's engaged in a handshake toward him, making it seem as if he's playing a game of tug-of-war rather than carrying out a common ritual of greeting of agreement. These concerns are likely to pervade the discussion between Trump and Merkel.
Trump and the German chancellor seemed on amicable enough terms when Merkel first arrived at the White House, shaking hands and exchanging pleasantries as the German leader stepped from her auto. He said "many nations owe vast sums of money from past years and it is very unfair to the United States".
The polar opposites met in Washington for the first time since Trump assumed office in January, and the face-to-face was sure to be filled with its share of tense exchanges behind closed doors.
The jab was a reference to reports in 2013 that the National Security Agency, under President Barack Obama, had been intercepting Merkel's phone calls and spying on German officials. Germany now spends 1.2 percent of GDP and remains reticent on defense matters due to its wartime past.
However, only a handful of the 28 members actually meet that target.
Ultimately, members' contributions are based on each nation's capability. President Trump should take this opportunity to reaffirm the US commitment to this important alliance.
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. It is part of our treaty commitment. The U.S. trade deficit with Germany was $64.9 billion past year, the lowest since 2009, according to the Commerce Department. The increased defense budget, however, will represent only 1.2 percent of the country's GDP.
"The essential point is, yes, Europe needs to pay more". "But because their security requires it".
"Even though we now see the likelihood of a trade war between the United States and Europe as small, the topic is still present and not completely off the table", Mattes wrote in a column in the Handelsblatt business daily. "Keeping Europe whole, free, and at peace, is vital USA interest".
Germany might find itself under more pressure to increase military funding if those four other nations made a decision to back Trump's criticism.
"As far as wiretapping, I guess by this past administration, at least we have something in common, perhaps", he said to laughter as Merkel appeared aghast before regaining her composure. German chancellors have a long tradition of taking groups of business leaders along with them on trips to important countries. Trump prefaced his defense spending statement by lashing out at the news media.
He continued: "You shouldn't be talking to me, you should be talking to Fox".
Trade is "a very big thing on the agenda for her", said Fran Burwell, vice president at the Atlantic Council.