Now only three European countries hit the two percent target, and while alliance officials are hopeful that four more will join the list by the July 11-12 summit, it is unlikely to satisfy Trump.
"Instead of viewing it that way, he views it as "The U.S. has been played"...and it's always this 'They're laughing at us, '" he added. "I don't know how much protection we get from protecting you".
"I believe the president is lining us up with an authoritarian dictator, instead of with democracies that promote economic and political freedom", the Washington Democrat told CNN.
Jon Huntsman Jr., Trump's ambassador to Moscow, hinted that the US president takes a tougher line on Putin in private, telling reporters, "The president will continue to hold Russian Federation accountable for its malign activities".
"What people are anxious about this trip is he'll have equally hard interactions with his North Atlantic Treaty Organisation counterparts", including Merkel and Canadian Prime Minister Justin Trudeau, said James Goldgeier, a visiting senior fellow at the Council on Foreign Relations and professor at American University, who is an expert in North Atlantic Treaty Organisation and security alliances.
The NATO summit is likely to be dominated by Trump's insistence that member nations step up and pay more for their joint defence.
As the investigation into ties between Russian Federation and trump continues, Trump's decision to meet one-on-one with Putin at an upcoming summit has drawn particular scrutiny, It seems Trump either does really have troubling ties to the Kremlin, or he doesn't mind acting in ways that make it look that way.
Trump has drawn criticism from members of both parties since taking office for his hesitance to speak out against Putin and Russian Federation, particularly over its attempts to interfere in the 2016 election. But he also raised eyebrows about his mindset for the one-on-one summit, which will not feature any aides, when he tweeted this last month: "Russia continues to say they had nothing to do with Meddling in our Election!" Putin's aggressive foreign policy is a threat to both us and our allies.
"Prior presidents saw America's allies as enhancing US power and really enabling the United States in being the global leader that it has been for so long, especially compared to China and Russian Federation, which have very few allies", said Goldgeier.
Much of the rest of Trump's foreign policy is equally freaky.