President Trump on Thursday hinted that he may move to bring more of the F-35 supply chain to the United States, citing what he called the “stupidity” of having work done overseas.

Trump, who made the remarks during an interview with Fox Business Network’s Maria Bartiromo, was asked whether he would incentivize U.S. companies to do more work domestically instead of relying on supply chains abroad.

“I could tell you hundreds of stories of the stupidity that I’ve seen. As an example, we make a fighter jet. It’s a certain fighter jet, I won’t tell you which, but it happens to be the F-35,” he replied.

“It’s a great jet, and we make parts for this jet all over the world. We make them in Turkey, we make them here, we make them there,” Trump added. “The problem is, if we have a problem with a country, you can’t make the jet. We get parts from all over the place. It’s so crazy. We should make everything in the United States.”

Pressed by Bartiromo on whether companies would move production of the F-35 stateside, Trump said, “We’re doing it because I’m changing all those policies.”

He did not provide further details.

It was not clear whether or how Trump would be able to bring international work on the Lockheed Martin-made F-35 to the United States.

Defense Department spokesman Lt. Col. Mike Andrews said the Pentagon “has no comment” on Trump’s remarks and referred questions to the White House.

But he said the Defense Department “remains fully committed to the F-35 program, and maintaining a competitive edge with its unique, unmatched 5th generation capabilities.”

Lockheed Martin, meanwhile, referred all questions to the Pentagon.

Trump’s desire to shift all F-35 work to the United States would be particularly difficult as the Joint Strike Fighter program was designed to be collaborative effort among several countries.

The U.S. military originally partnered with eight other countries to produce the advanced aircraft for itself as well as participating nations: Australia, Canada, Denmark, Italy, the Netherlands, Norway, Turkey and the United Kingdom. The countries helped pay for developing the jet, producing parts and assembling the aircraft.

NATO ally Turkey was kicked out of the program last year after it took possession of the Russian-made S-400 anti-aircraft surface-to-air missile system, which the United States fears could be used to glean sensitive information from F-35 technology.