"The aim of this meeting is to begin setting right the negative state of bilateral relations, to agree on concrete measures to improve them and to establish a more or less acceptable level of trust", Ushakov said. "It's been wonderful to see the level of spirit in that room".
Since last year's North Atlantic Treaty Organisation summit allies had added $US41bn to their budgets, he said, and now they would redouble their efforts.
Mr Trump said he would be discussing the civil war in Syria, the conflict in Ukraine, as well as allegations of Russian meddling in the 2016 United States election. He said that two-thirds of the allied states had made plans to reach two per cent of GDP in 2024 and eight members had already achieved it. Add Donald Trump as an interest to stay up to date on the latest Donald Trump news, video, and analysis from ABC News.
It was a classic Trump performance - bluster, confrontation and demands followed by a unilateral declaration of victory - but his claim was quickly dismissed by the leaders of Italy and France, who disputed they had made any new pledges for increasing spending.
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.
"Whatever you do, it's OK with me", he said after talks with May, adding: "The only thing I ask of Theresa is to make sure we can trade".
He touted his government's long-awaited defence policy review, released last June, as the answer to Trump's latest demands for more spending from North Atlantic Treaty Organisation allies.
Despite that, Stoltenberg had been forced to call an extraordinary session of all 29 allies to discuss Trump's demands, in what officials said was one of the first of its kind at a North Atlantic Treaty Organisation summit for a decade.
Trump is set to meet his Russian counterpart Vladimir Putin for their first ever summit in Helsinki on July 16 though Moscow said the former's remarks were unlikely to affect what was always going to be a hard summit between two countries known to have several differences, the Reuters report added.
Earlier Friday, Trump said he would question Putin about Russia's election meddling when the two meet in Helsinki. We have bben following a very bright path for the last 10 years and every summit is a step forward for us, including this summit where the leaders of the North Atlantic Treaty Organisation member states assembled and gave the current events of Ukraine and Georgia a suitable name- Russian aggression and the occupation of independent states.
The Kremlin has denied that the Russian government interfered in the USA election.
Following Thursday's emergency session of North Atlantic Treaty Organisation members, Trump declared the military alliance to be "very unified, very strong, no problem".
Arizona U.S. Sen. John McCain echoed the sentiment.
"Ultimately, that will be going up quite a bit higher than that", he said.
Air Force One has landed at London Stansted Airport, where Trump is beginning a four-day visit to the country.
From Brussels, he flew to Britain where the government is in crisis over Brexit and where tensions with Russian Federation have spiked after London blamed Moscow for the death this month of a British woman from contact with the Novichok nerve agent.