Secretary of State Rex Tillerson on Friday reportedly gave NATO allies two months to either meet the group’s defense budget guidelines or offer up a schedule for doing so.

"Allies that do not have a concrete plan to spend 2 percent of [gross domestic product] on defense by 2024 need to establish one now. Allies that have a plan to reach the 2 percent guideline need to accelerate efforts and show results," Tillerson said in Brussels, according to The Associated Press.

It was Tillerson’s first meeting with his counterparts from NATO, which President Trump has repeatedly faulted for failing to live up to its defense spending commitments.

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Only four European nations met the 2014 defense goal of 2 percent spending of total GDP: the United Kingdom, Poland, Greece and Estonia.

On the campaign trail, Trump repeatedly called out NATO members for falling short of their commitments, and even floated backing down on treaty obligations.

Tillerson made it clear on Friday, however, the U.S. would defend its allies.

“We understand that a threat against one of us is a threat against all of us, and we will respond accordingly,” he said. “We will uphold the agreements we have made to defend our allies.”