Within NATO, only the United States, the Netherlands and Germany possess Patriot missiles. The Netherlands has sent Patriots to Turkey twice before during both Gulf wars in 1991 and 2003.

Turkey is reluctant to be drawn into the fighting, but the proximity of Syrian bombing raids to its border is straining its nerves. It has repeatedly scrambled fighter jets along the frontier and responded in kind to stray Syrian shells that have crossed into its territory.

Turkey -- a major backer of Syria’s opposition -- is worried about its neighbor’s chemical weapons, the refugee crisis on its border, and what it says is Syrian support for Kurdish militants on its own soil.

(Writing by Jonathon Burch; Editing by Nick Tattersall and Hugh Lawson)