NATO chief Anders Fogh Rasmussen says the alliance would consider a request from Turkey to deploy Patriot anti-missile batteries along its border with Syria.
Rasmussen said Monday the North Atlantic Treaty Organization had received no formal request from member-state Turkey so far but added that if one was made, "we will consider that as a matter of urgency."
German Defense Minister Thomas de Maiziere said he expected a request later Monday from Turkey, whose border villages have been hit by artillery fire as forces loyal to Syrian President Bashar al-Assad battle rebels seeking his ouster.
Rasmussen said NATO has plans ready to defend and protect Turkey if needed but those do not currently include imposing a no-fly zone with Patriot missile back-up. He said any Patriot deployment would be a "purely defensive measure to defend Turkey."
Ankara, a one-time Damascus ally, said last week it was in talks with NATO about the Patriots but had not made any formal request.
Also Monday, the president of Syria's new opposition coalition was quoted by Egypt's official news agency as saying the group has decided to make Egypt its headquarters.
But a group of extremist Islamist factions in Syria rejected the National Coalition for Opposition and Revolutionary Forces, formed earlier this month in Qatar, saying in a video statement they have formed an "Islamic state" in the embattled city of Aleppo.
The statement by 13 radical factions that was posted on a militant website late Sunday suggested the extremist elements - including the al-Qaida-inspired al-Nusra Front - are suspicious of the new coalition.
Syrian rebels said they captured a large special forces base on a main road between the city of Aleppo and the Turkish border on Sunday.