"Some are at 2 per cent, others have agreed definitely to go to 2 per cent, and some are going back to get the approval, and which they will get to go to 2 per cent", he said.
Still, by the time it was over he was ebullient, saying that European allies and Canada had "really stepped up their commitment" - and intimating that his relentless hectoring had forced other allies to spend more than NATO's long-term goal of 2 percent of GDP on defense.
Still, European economies have been growing recently, making the 2 percent of GDP target ever harder to achieve, and Trump's spending demand is at least in part aimed at drumming up business for the US defense industry.
Instead, a series of events - a black-tie dinner with business leaders, a meeting with Prime Minister Theresa May and an audience with Queen Elizabeth II - will happen outside the bustling city, where Mayor Sadiq Khan has been in a verbal battle with Trump.
Some will say that an unpredictable president such as Donald Trump is the only American leader who could achieve these outcomes - because the fear is real.
"The communique is clear", Macron said.
Just eight countries are forecast to reach the two per cent goal this year, and 15 by 2024.
North Atlantic Treaty Organisation members reiterated that no new decisions about spending were made at the summit.
Asked about pressures on countries with weaker finances, he said, "We have many wealthy countries with us today but we have some that aren't so wealthy and they did ask me if they could buy the military equipment, and could I help them out, and we will help them out a little bit", he told a news conference.
Earlier Foreign Secretary Jeremy Hunt backed Mr Trump's demands for allies which were not hitting the 2% target to do more. "Very unified, very strong, no problem".
Stoltenberg, a former Norwegian premier who Trump said gave him "total credit" for a successful summit, told reporters: "We had a very frank and open discussion ... I'm very strong on immigration".
Trump reportedly targeted Germany the most during the meeting, and even accused German Chancellor Angela Merkel of being "totally controlled by Russia", referring to heavy imports of Russian gas.
Trump said he made his anger clear to allies on Wednesday.
When asked if this was true, Trump did not directly deny it. "If he said something on the side I don't know", Conte said. He is also scheduled to hold his first summit with Russian President Vladimir Putin in Helsinki, Finland, on July 16, 2018. Leaders also criticized Russia's "hybrid actions" including attempted interference in numerous elections, "widespread disinformation campaigns, and malicious cyber activities".
Trump said he wanted "peace all over the world, that's my goal", and he wanted to achieve this by building up the military, with his dream to have the best military equipment in the world and never have to use it.
The alliance was founded upon the notion of collective defense, meaning an attack on one member state is considered an attack on all of them.
"What you spend on a military budget doesn't necessarily automatically lead to greater capacity to contribute to NATO's defence", he said.
"The United States stands with the repressed and continues to encourage despotic regimes to turn away from authoritarianism and respect the God-given rights of life and liberty", he added. The president said the 2 percent threshold would be met "in a relatively short number of years". "They're going to up it at levels they've never thought of before".