President Donald Trump urged members of the NATO alliance to start paying their fair share Thursday in Brussels, pointing out that their failures were hurting American taxpayers.

“NATO members must finally contribute their fair share and meet their financial obligations,” Trump said, pointing out that 23 of 28 members were still not paying enough money for their national defense and even owed a great deal of money.

“This is not fair to the people and taxpayers of the United States,” Trump said, reminding the foreign leaders that the United States spent more on defense than all the other nations together.

The president made his remarks during the unveiling of a memorial which featured the Berlin Wall and a section of one of the Twin Towers that were destroyed by terrorists on 9/11.

Trump admitted that his call was “very, very direct,” but essential for keeping the alliance together.

“We have to make up for the many years lost,” Trump said. “Two percent is the bare minimum for confronting today’s very real and very vicious threats.”

He also alluded to the cost of the new NATO headquarters building, suggesting that it was another expense shouldered by the American taxpayer.

“I never asked once what the new NATO headquarters cost, I refuse to do that, but it is beautiful,” he said.