Later, when asked if he sees Putin as a friend or a foe, Trump said he sees the Russian leader as a "competitor".
This spring Tusk said that "Someone could even think 'with friends like that, who needs enemies,"' after Trump first threatened to slap tariffs on European Union steel and aluminum exports and reneged on an agreement to stop Iran from developing nuclear weapons.
Speaking to reporters at the White House before leaving on the week-long trip, Trump repeated his criticism of North Atlantic Treaty Organisation allies for not spending enough on their defense and pointed to the political tensions in Britain over the government's Brexit plans.
"The fact that a Putin-Trump meeting will happen says only one thing: that for all its hysteria, the United States is not able to isolate or ignore Russia", said Alexei Pushkov, a prominent Russian senator from the ruling United Russia party.
"Getting ready to leave for Europe". While some diplomats say they are concerned Trump could condition U.S. help on the 2% spending threshold, others worry the President could scale back a planned funding increase for a European deterrence program.
The American president made clear that he did not necessarily see his nominal European allies as preferable to Russian Federation or China, whom Washington has both at times threatened with military action.
Prime Minister Justin Trudeau managed to steer clear of Donald Trump's blast radius Wednesday as the two leaders converged for the first day of the NATO leaders' summit, opting to meet informally to discuss North American trade irritants instead of the burning issue of defence spending.
Answering questions from reporters on the lawn of the White House as he and his wife Melania prepared to board the Marine One presidential helicopter, Mr Trump said that the United Kingdom "certainly has a lot of things going on".
"Just look at the chart", Trump said at the breakfast.
In a letter last month, U.S. Secretary of Defence Jim Mattis wrote to British Defence Secretary Gavin Williamson threatening to replace Britain with France as Washington's closest military ally if London did not further increase military spending.
Speaking to reporters Tuesday from the White House before departing Washington for Europe, Trump says of the 69-year old trans-Atlantic mutual defense pact, "Frankly it helps them a lot more than it helps us". Yet the USA chooses to spend more on defense and not all of the funds go towards NATO-related expenses. The U.S.is paying for Europe's protection, then loses billions on Trade.
The two tweets represented two major topics of criticism Trump has long held against United States allies across the Atlantic: one is his belief that the European Union erected trade barriers against the USA and as a result won surplus in the trade of goods, and the other that European members of NATO are not spending enough on defence.
"America does not have, and will not have a better ally than Europe", Tusk said at a joint European Union. One, on the US East Coast, will protect transatlantic sea lanes and another, in Germany, will run logistics to make sure the alliance can respond quickly to threats. "America, appreciate your allies, after all you don't have that many".
"The best-case scenario is that it's just rhetoric", the European official said of Trump's comments about a USA willingness to maintain its commitment to Europe.
But Trump's unpredictability and capacity to cause ructions among Washington's allies will give Ukraine pause for thought.
Trump pressed on: "If you look at it, Germany is a captive of Russian Federation, because they supply -- they got rid of their coal plants, got rid of their nuclear, they're getting so much of the oil and gas from Russian Federation".
"Some are at 2 percent, others have agreed definitely to go to 2 percent, and some are going back to get the approval, and which they will get to go to 2 percent", he said.
Tusk, a former Polish prime minister who is president of the European Council, let it be known before the 2016 US presidential election that he thought "one Donald is more than enough!"
"It's very sad when Germany makes a massive oil and gas deal with Russia where we're supposed to be guarding against Russia and Germany goes out and pays billions and billions of dollars a year to Russia", Trump said before meeting with NATO Secretary General Jens Stoltenberg on Wednesday morning.
He said that of the high-stakes meetings of his trip, "Putin may be the easiest of them all".
Andrew Holland, the director of the American Security Projects' Energy & Infrastructure Studies program, says a U.S. president's rhetoric matters deeply when it comes to foreign policy. All but four countries still fall short of meeting the goal, but it is not a binding legal commitment.