NATO Secretary-General Mark Rutte met President Donald Trump at the White House to ease mounting strains over the war in Iran and growing tensions inside the alliance ahead of a July summit in Ankara.

Rutte used a mix of reassurance and messaging aimed at Trump’s concerns, telling him that examples of European reluctance to support Washington were “isolated cases.” He also presented data showing that NATO allies have increased defense spending since Trump took office in 2017, arguing the alliance has largely been there when the U.S. needed support.

In the meeting, Rutte highlighted how thousands of U.S. military planes operated from bases in Europe during the Iran conflict, portraying that cooperation as evidence of NATO backing. Trump, a longstanding NATO critic who has called the alliance a “paper tiger,” appeared unconvinced but praised Rutte for his efforts.

The discussion came as Trump has grown angry at what he views as insufficient allied support for his Iran strategy and related efforts tied to the Strait of Hormuz, after an incident on Feb. 28 disrupted the major shipping route. With relations between Washington and NATO worsening in recent months—including Trump openly questioning NATO’s mutual defense value—Rutte’s role has included preventing sharp moments from turning into lasting crises.