President Donald Trump says the United States may take action on trade with those countries not contributing enough to NATO.
Trump, fresh from a trip to London for a meeting with fellow leaders of the North Atlantic Treaty Organisation, has been pushing member countries to contribute more to the organisation.
He said more countries were getting close to the goal of two per cent of the Gross Domestic Product for NATO contributions, but others were not.
"A lot of countries are close and getting closer. And some are really not close, and we may do things having to do with trade. It's not fair that they get US protection and they're not putting up their money," Trump said said on Thursday.
Trump and French leader Emmanuel Macron clashed over the future of NATO on Tuesday before a summit intended to celebrate the 70th anniversary of the Western military alliance.
In sharp exchanges underlining discord in a transatlantic bloc hailed by many as the most successful military pact in history, Trump demanded that Europe pay more for its collective defence and make concessions to US interests on trade.
But he also was upbeat about the alliance on Thursday, saying his meetings went well and that "NATO is in very, very good shape and the relationships with other countries are really extraordinary."
However, Trump called Justin Trudeau "two-faced" over a video in which the Canadian PM appears to mock him at a meeting of other NATO leaders at a Buckingham Palace reception on Tuesday evening,.
Video footage showed Trudeau, UK PM Boris Johnson and French leader Emmanuel Macron discussing an impromptu press conference held by Trump during the visit in the UK capital.
Australian Associated Press