President Trump unloaded on Western European allies as disloyal partners who were “not there for us” during the Iran conflict despite America’s largesse in bolstering mutual defense, marking a frosty start to NATO meetings on Tuesday.

Mr. Trump’s shot at America’s military partners came at the start of a two-day summit in Ankara, Turkey, which will pivot on commitments to defense spending and whether Ukraine and Russia can settle their 4-year-old war.

“I’ve long said that we help them, but I’m not sure they’d be there for us,” Mr. Trump said of the allies while he sat down with Turkish President Recep Tayyip Erdogan and pointed to NATO’s lack of cooperation with his campaign against Iran. “Italy turned us down and Germany turned us down and France turned us down. And that’s OK, but why are we spending hundreds of billions of dollars, and they’re not there for us? We’ve always been there for them.”

Mr. Trump’s tense relationship with NATO isn’t new. He sparred with allies over their lackluster defense spending, overseas troop placements and Europe’s overreliance on Russian oil and gas during his first term.

But tensions were supercharged this term by spats over tariffs, the Iran war and control of the Arctic.

Mr. Trump on Tuesday revived his complaint that Greenland is controlled by Denmark instead of the U.S., plus attacked Europe for losing its grip.

“With all that money we spend to help them with Russia, we don’t have to spend any money — we could remove all of our soldiers out of Europe,” he said.

“As you probably noticed, Europe’s a very different place than it was 20 years ago,” he added. “With immigration and energy. If they’re not careful with those two things, you’re not going to have a Europe anymore.”

Mr. Trump contrasted the West’s perceived disloyalty with Turkey, which is poised to regain access to the American F-35 program despite being booted from it in the first Trump administration.

The president said Ankara has been “frankly, more helpful to the United States than many other, more traditional countries.”

“They could have gotten into the fight,” Mr. Trump said of Turkey, adding that Mr. Erdogan is not friendly with Israel and might have intervened in the U.S.-Israeli campaign against Tehran. “Maybe they didn’t do that because of me.”

Mr. Trump chafed at European allies’ reluctance to provide air bases and other assistance during Operation Epic Fury, though Western countries said they were caught off guard by the U.S.-Israeli bombardment.

Mr. Trump says he’s the one who solidified NATO by prodding each member to meet last year’s commitment to increase defense spending to at least 5% of gross domestic product.

The president now wants a progress report on each country’s commitment to that goal.

Hoping to show its commitment to spending, NATO announced a deal Tuesday to replace early warning radar surveillance planes that are around 50 years old.

“I am proud that NATO has chosen the Swedish platform GlobalEye as the Alliance’s new platform for airborne early warning and control,” Swedish Prime Minister Ulf Kristersson said on X. “GlobalEye will contribute greatly to core needs for our collective defense.”

NATO Secretary-General Mark Rutte also said the alliance will commit to “tens of billions” of dollars’ worth of defense contracts during the summit.

Meanwhile, the host nation’s defense capabilities were front and center in Mr. Trump’s sit-down with Mr. Erdogan.

Mr. Trump said inviting Ankara back into the F-35 sphere is “something certainly we would consider.”

“Why wouldn’t we do that?” he said. “Turkey, in many ways, has been much more loyal than other countries that we think would be loyal.”

Turkey used to be a member of the F-35 program. It was booted in 2019 because it acquired the Russian S-400 air defense system, which Washington viewed as a security risk.

The F-35 is considered a highly advanced stealth fighter. Its radar and sensors give pilots enhanced capability and help the plane serve as a key node in battle networks with other fighters.

Mr. Trump must work through a series of legal hurdles and congressional restrictions before granting Turkey access, including assurance that the technology will not be shared with Russia or third parties.

“I have no concerns about anything having to do with Turkey,” Mr. Trump said.

“Turkey has become, under the president, a very powerful country, militarily. People don’t know how powerful, actually,” he said. “They really are somebody to be reckoned with.”

Mr. Erdogan greeted Mr. Trump on the tarmac when the president touched down at Etimesgut Air Base early Tuesday.

They also enjoyed a lavish state arrival ceremony and honor guard review at the Bestepe presidential palace that featured troops and patriotic selections from a band.

On Wednesday, Mr. Trump will meet with Ukrainian President Volodymyr Zelenskyy and Syrian President Ahmad al-Sharaa before his scheduled news conference and departure.

Mr. Trump said he’s confident that Russia and Ukraine are closer to settling the war that began in February 2022.

The president said he’s concerned about the massive loss of life on both sides.