The European Union on Monday backed Canadian Prime Minister Justin Trudeau after U.S. President Donald Trump branded him "dishonest" and "weak" following a weekend Group of Seven summit of leaders, ABC News reported.

European Commission spokesman Margaritis Schinas said the EU "stands fully behind" the joint statement issued at the end of the G-7.

Trump agreed to a statement on trade but withdrew from it later. He complained he was blindsided by Trudeau's criticism of his tariff threats during the premier's summit-ending news conference.

"The European Union will continue to stand up for an international, rules-based, multilateral system," Schinas said.

He added that EU Commission President Jean-Claude Juncker thanks Trudeau "for the excellent preparation and chairing of this challenging summit."

In London, Mayor Sadiq Khan said he hopes Trump will reconsider policies such as the recent increase in tariffs on steel and aluminum from Europe, China, Mexico, Canada and elsewhere.

"I would hope that he would reflect on what his closest allies are saying... Not just the U.K. but Canada, Germany, Japan — these aren't foes, these are friends," he told The Associated Press at a technology conference..

"When there's a trade war, everyone's a loser," Khan said