BELGRADE, Serbia (AP) — Serbia is considering the purchase of a modern Chinese air defense missile system as the United States warned that such deals with Beijing could jeopardize the Balkan country’s proclaimed European Union membership goals. Serbian President Aleksandar Vucic said Tuesday that “we were thinking, but we have not yet purchased” the FK-3 system, the export version of the Chinese last-generation, medium range HQ-22 anti-aircraft system. Serbia, which has been beefing up its military mainly with Russian aircraft and armored vehicles, last month received six Chinese CH-92A attack and reconnaissance drones. That made Serbia the first European country to deploy the Chinese unmanned aerial vehicles.