Turkish President Recep Tayyip Erdogan said Tuesday that Ankara would not withdraw from a deal made with Russia to buy an S-400 missile defense system despite US threats.
"We have made an agreement (with Russia). We are determined," Erdogan was quoted as saying by the official Anadolu news agency.
"There is nothing like backtracking from that," he told journalists after prayers at an Istanbul mosque.
Last week, a top Pentagon official said the consequences would be "devastating" for Turkey's joint F-35 fighter program and its cooperation with NATO if the country went ahead with plans to buy the Russian anti-aircraft weapon system.
Kathryn Wheelbarger, Acting Assistant Secretary of Defense for International Security Affairs, said the planned purchase would damage Turkey's ability to work with the Western alliance, and force Washington to hit the country with sanctions against arms deals with Russia.
She said the US administration, even if it does not want to punish Turkey for the purchase, could be forced to do so by a Congress unsympathetic to Ankara.
US officials said they expect Turkey to opt for the American Patriot missiles instead, arguing that would then allow the F-35 program to continue.
Turkey plans to buy 100 US F-35s, and some Turkish pilots have already started training with counterparts in the US.
Erdogan said Tuesday he told the US that Ankara would take steps to buy the Patriots only if its conditions of delivery were as positive as Russia's.
"But unfortunately we haven't received a positive proposal from the American side on the subject of Patriots like the S400s from Russia," he added.