BELGRADE, Serbia (AP) — Serbia has displayed a recently delivered sophisticated Chinese anti-aircraft missile system at an event at a military airport near Belgrade, the capital. That has raised concerns in the West and among some of Serbia’s neighbors that an arms buildup in the Balkans could threaten fragile peace in the region. The HQ-22 surface-to-air system was delivered last month by a dozen Chinese Air Force Y-20 transport planes in what was believed to be the largest ever airlift delivery of Chinese arms to Europe. Although Serbia officially seeks membership in the European Union, it has been arming itself mostly with Russian and Chinese weapons.