On day two he stated that the United States' commitment to the alliance remains "very strong".
The summit in Brussels is shaping up as the alliance's most hard in years, against a backdrop of deepening transatlantic tensions in fields ranging from trade to energy and defence. Trump wants the spending to go up to 4% of GDP, which is more than even the USA now spends on defense.
And as the leader of the bigger military power in the world they have to continue to work with Donald Trump and try to find a way to keep him happy.
As he flew off to the United Kingdom on Thursday for the next leg of his European tour, it was left to President Emmanuel Macron of France to correct the record following Trump's freewheeling press conference in which he claimed to have pushed allies into new defence spending commitments.
Nato Secretary General Jens Stoltenberg took a more diplomatic approach on the spending row, saying that Trump was having an "impact" while refusing to confirm any increase beyond what was agreed in the statement.
And the president's declaration was also directly contradicted by one of his closest personal allies, French President Emanuel Macron. But I will tell you this: at a certain point they're going to call me they're going to say "Let's make a deal".
"Based on just the way things are shaping up, I think a non-eventful Helsinki meeting might be best for our country", Republican Senator Bob Corker, chairman of the Foreign Relations committee, told Reuters.
McCain then ticked off a series by transgressions by Putin, including the "attack" on the US election and efforts "to undermine democratic institutions throughout the world".
President Donald Trump to visit Windsor on United Kingdom tour
His criticism of Britain's anti-terror policies after a series of attacks in 2017 also did not go down well. Melania Trump's spokesperson did not immediately respond to a request for comment.
Before leaving on Thursday for a visit to the United Kingdom, Trump called US commitment to the alliance "very strong", and referred to the two-day summit as "fantastic" characterized by "a great collegial spirit".
Mr. Trump's comments came ahead of his summit on Monday with Russian President Vladimir Putin in Helsinki, though the Kremlin said they were unlikely to have an impact on what was always going to be a hard meeting due to the number of disagreements between the two countries.
During his 28 hours there, Trump had disparaged longtime North Atlantic Treaty Organisation allies, cast doubt on his commitment to the mutual-defence organization and sent the 29-member pact into a frenzied emergency session. "The current commitment is to reach two percent by 2024 but with get-out terms that would allow some to stretch it out to 2030".
At the same breakfast (and on several other occasions later in the day), Trump blasted German Chancellor Angela Merkel for an energy deal her country has with Russian Federation, saying they are "totally controlled by Russian Federation", and a "captive" of the country.
"[It] will definitely affect trade with the United States, unfortunately in a negative way", he added, noting how the U.S. already has "enough difficulty with the European Union".
Most had written off the day as much duller than the previous - when the US President had lambasted German Chancellor Angela Merkel as a captive of Russian Federation. That's still true today; this year Congress casually flung another $61 billion - roughly enough to pay for free tuition in every public college and university in the country - on top of the already-mountainous military budget.
Of the 29-member alliance, only the UK, Poland, Estonia and debt-ridden Greece met the benchmark in 2017.
"We understand this U.S. president is very serious about defence spending and this is having an impact", Stoltenberg said.