The Trump administration has repeatedly told Turkey that it will be cut off from buying F-35s if it buys the S-400 Russian air defense system because it's incompatible with NATO defenses and could jeopardize sensitive information about F-35 technologies. Turkey is a member of NATO.
Trump blamed the Obama administration for never reaching a deal to sell an American missile defense system to Turkey.
He says Turkey had ordered more than 100 F-35s but because it bought a Russian missile system, the U.S. can't sell it billions of dollars' worth of aircraft.
Trump spoke Tuesday during a Cabinet meeting at the White House.