WASHINGTON (Reuters) - U.S. President Donald Trump said on Friday that he backs the NATO charter’s demand that all members be prepared to defend each other, weeks after jarring allies by not restating U.S. support for the agreement.

At a joint news conference with Romanian President Klaus Iohannis, Trump said he supports the NATO charter’s Article 5, the requirement that each member of the alliance defend each other if they come under attack.

During a visit to NATO headquarters last month in Brussels, Trump had pointedly not mentioned U.S. support for the critical portion of the NATO charter. He used his speech there to demand that members pay more for the alliance’s defense.

A senior White House official later had said the United States does in fact support Article 5 simply by agreeing to the terms of the charter.

But having not mentioned it himself, Trump sowed some doubts among allies and the ensuing controversy prompted Vice President Mike Pence to later express explicit U.S. support for the charter.

Senior aides to Trump had tried to get a statement of explicit support for Article 5 in the president’s NATO speech but it was not included, a senior administration official said.

“I’m committing the United States to Article 5 and certainly we are there to protect and that’s one of the reasons that I want people to make sure we have a very, very strong force by paying the kind of money necessary to have that force,” Trump said.

“But yes, absolutely I’d be committed to Article 5,” he said.