Defense Secretary ​Pete Hegseth announced a Pentagon-led review of American forces in Europe on Thursday, and criticized some NATO allies over defense spending and reluctance to participate in the Iran war.

“It’s a ​review that some countries ‌will ⁠fail, and others will pass with flying colors,” Hegseth ​told ​NATO ⁠defense ministers in Brussels, Reuters reported.

Hegseth added that the six-month review is designed to “ensure that NATO is moving fast and irreversibly” toward taking primary responsibility for the defense of Europe.

He also said it was “shameful” that European allies refused to give U.S. forces access to bases to strike Iran.

NATO member states committed to hiking defense spending last year, following pressure from the Trump administration for Europe to shoulder a greater responsibility for its own security.

Hegseth said in May that the U.S. demands a minimum defense spending commitment of 3.5% of gross domestic product from its allies and partners, adding that Washington will prioritize working with these “model allies.”

Last month, he praised countries such as the Philippines, Australia, Indonesia, Malaysia and Singapore for stepping up and sharing the burdens of defense and alliances, while continuing to lambast Europe.

President Donald Trump has remained critical of NATO, threatening to withdraw the U.S. from the alliance over its reluctance to assist with the reopening of the Strait of Hormuz.

In dollar terms, the U.S. remains the alliance’s biggest spender on defense by far. NATO data shows that the U.S. spent an estimated $845 billion on defense last year, dwarfing the $559 billion spent by the rest of the alliance combined.

— CNBC’s Lim Hui Jie and Chloe Taylor also contributed to this report.