U.S. National Security Advisor Mike Waltz speaks during the daily press briefing in the Brady Briefing Room of the White House in Washington, D.C., Feb. 20. AFP-Yonhap

U.S. President Donald Trump's top security adviser called Thursday for all member states of the North Atlantic Treaty Organization (NATO) to meet their commitment to spend 2 percent of their gross domestic product (GDP) on defense before a NATO summit set for June.

National Security Adviser Mike Waltz made the call as Trump has said that NATO member states should spend 5 percent of their GDP beyond the 2 percent guideline set in 2014.

"The fact that we are going to enter into a NATO summit this June with a third of our NATO allies still not meeting the 2 percent minimum — a commitment they made a decade ago, literally a decade ago — with a war on their doorstep, the largest war that they're all extremely concerned about," Waltz said during a press briefing.

"But ... somebody else needs to pay. We've got other domestic priorities. That's unacceptable," he added.

The official went on to say that before this year's NATO summit, the 2 percent guideline needs to be fulfilled by all NATO allies.

"We need to be at 100 percent in this June, in the NATO summit, and then let's talk about exceeding it, which is what President Trump has been talking about — 5 percent of GDP," he said. "Europe needs to step up for their own defense as a partner, and we can be friends and allies and have those tough conversations."

Waltz reiterated that American taxpayers continue to "bear the burden, not only of the cost of the war in Ukraine, but of the defense of Europe."

"We fully support our NATO allies. We fully support the Article 5 commitment," he said, referring to the collective defense clause. "But it's time for our European allies to step up."

The official's remarks came amid lingering concerns that Trump could demand South Korea increase its spending for the stationing of the 28,500-strong U.S. Forces Korea (USFK).

In October, Seoul and Washington struck a defense cost-sharing deal, called the Special Measures Agreement (SMA). Under the deal for the 2026-2030 period, Seoul is to pay 1.52 trillion won ($1.06 billion) next year, up from 1.4 trillion won this year.

After the conclusion of SMA negotiations, Trump said during a presidential campaign that South Korea would be paying $10 billion a year for the upkeep of USFK if he had been in the White House. He also described the Asian ally as a "money machine." (Yonhap)