NATO foreign ministers will agree on Tuesday to send Patriot missiles to beef up Turkey's air defences and calm Turkey's fears that it could come under missile attack, possibly with chemical weapons, from Syria, diplomats said.

Turkey last month asked NATO for Patriots, which can be used to intercept missiles and planes, after weeks of talks with allies about how to shore up security on its 900-km (560-mile) border with Syria, which is immersed in civil war.