WASHINGTON (AP) — NATO Secretary-General Mark Rutte met with President Donald Trump on Wednesday, pressing the case for a military alliance that the volatile U.S. leader has sharply criticized as the Pentagon reviews the size of the U.S. military footprint in Europe.

READ MORE: Hegseth appears out of step in criticisms of NATO allies

Trump has slammed NATO, arguing the U.S. carries more than its fair share of military spending. But his grievances have been louder since the Iran war as he fumed over the fact that some member countries ignored his call to help him restart oil trade through the shuttered Strait of Hormuz.

Trump has renewed his threats to leave the 77-year-old alliance, raising the stakes before the NATO leaders' summit in Turkey next month. But Rutte, who has become known as a Trump whisperer for his ability to charm the president, was looking to appease him Wednesday.

Meeting with Trump in the Oval Office, Rutte pushed back gently, saying, "I know there have been isolated cases about which you are really disappointed, but generally speaking, your European allies have been there with you."

Rutte also noted that 4,000 to 5,000 U.S. planes took off from bases in Europe before Iran and the U.S. agreed to a ceasefire.

That followed Trump's comment, while introducing Rutte, that "they weren't too nice to us in our recent little military skirmish."

Defense Department conducting a review of American forces in Europe

The visit, Rutte's fifth since Trump returned to power last year, comes after U.S. Defense Secretary Pete Hegseth last week lashed out at allies during a meeting at NATO headquarters in Brussels. His department is in the midst of a six-month review of U.S. forces in Europe.

Hegseth echoed some of Trump's critiques, faulting European allies for not letting the U.S. use bases in Europe to attack Iran. NATO allies were not consulted about the war before the U.S. launched it with Israel on Feb. 28, and some have been openly critical of Trump's strategy.

Trump argues that NATO allies were not there for the U.S. and suggested leaving the alliance, which was founded in 1949 to counter the Cold War threat posed to European security by the Soviet Union. At the heart of their treaty is a mutual defense agreement in which an attack on one is considered an attack on all. The only time it has been invoked was in 2001, to support the United States after the Sept. 11 attacks on New York and Washington.

The Pentagon's warning that it will reduce its military presence in Europe to focus on threats elsewhere was the latest upheaval for the 32-member alliance since Trump returned to office.

The Republican leader stunned European allies last year when he threatened to annex Greenland, a semiautonomous island that is part of ally Denmark.

Earlier Wednesday, the leaders of five big European NATO allies — Germany, France, the U.K., Italy and Poland – met in Berlin to prepare for next month's summit in Ankara, and Rutte joined them remotely.

German Chancellor Friedrich Merz said in remarks to reporters that the Ankara summit also should send the message that "we will do our part when the conditions are in place" to support an Iran peace deal.

French President Emmanuel Macron said "we are in a moment of reconvergence between the Europeans and the Americans" and indicated that he hopes that will continue at the summit.

Flattering Trump is a key objective

A chief part of Rutte's mission these days is keeping the U.S. in NATO, and he's proven himself deft in the past at subduing Trump's frustrations.

Rutte frequently flatters the president, crediting him with getting NATO members to increase their defense spending. Trump last year pressured leaders to agree to invest 5% of their GDP annually on defense by 2035.

On Tuesday evening, Rutte appeared for an interview on Fox News Channel, of which Trump is known to be a dedicated viewer.

Rutte repeatedly praised Trump, emphasizing he is the leader of the NATO alliance and said of his efforts in Iran: "I'm completely behind him on this."

He said Trump's frustrations over the use of bases in Europe involved a few "isolated cases."

The lengths to which Rutte is willing to praise Trump have at times raised eyebrows, such as when he referred to the president as "daddy" during the alliance's summit last year.

He then sent him a fawning text message that employed one of Trump's favorite flourishes, capitalizing random words. "Europe is going to pay in a BIG way, as they should, and it will be your win," Rutte said.

Trump shared the private message on social media for the world to see.

He did it again in January, blasting out another Rutte message that closed with: "Can't wait to see you. Yours, Mark."

Associated Press writers Lorne Cook in Brussels and Geir Moulson in Berlin contributed to this report.