U.S. President Donald Trump has turned his frustration toward NATO as the Iran war intensifies, raising new concerns about the alliance’s future. European allies have refused to provide military support to reopen the Strait of Hormuz and, in some cases, denied U.S. aircraft access to their bases. In an interview with the British newspaper The Telegraph, Trump called NATO a “paper tiger” and said he is seriously considering withdrawing the United States from the alliance.

The tension is not new. Trump has previously labeled NATO “obsolete” and threatened to withhold protection from members that fail to increase defense spending. The situation has deepened as U.S. Secretary of State Marco Rubio warned that Washington might reconsider its NATO ties if European nations continue to block base access. Former U.S. ambassador Ivo Daalder said the crisis has shaken the alliance’s trust, calling it potentially NATO’s biggest challenge in history.

Despite the rift, U.K. Prime Minister Keir Starmer reaffirmed full commitment to NATO, and Secretary-General Mark Rutte argued that Trump’s pressure has strengthened the alliance. The upcoming NATO summit in Ankara this July is expected to test the alliance’s cohesion amid growing calls in Europe for greater defense autonomy.