NATO will consider "without delay" a request from member Turkey for a deployment of surface-to-air Patriot missiles to protect its troubled border with Syria, Alliance chief Anders Fogh Rasmussen said on Wednesday.

"I have received a letter from the Turkish government requesting the deployment of Patriot missiles," Rasmussen said in a statement.

"Such a deployment would augment Turkey's air defence capabilities to defend the population and territory of Turkey. It would contribute to the de-escalation of the crisis along NATO's south-eastern border.

"And it would be a concrete demonstration of alliance solidarity and resolve," the statement said. "Nato will discuss the Turkish request without delay."

Expected for several days, the request was welcomed at a meeting of NATO ambassadors who should give their approval in coming days, a diplomatic source told AFP.

Rasmussen said a team would visit Turkey as early as next week to conduct a site-survey for the possible deployment of Patriots.

"The security of the alliance is indivisible," Rasmussen said.

"NATO is fully committed to deterring against any threats and defending Turkey's territorial integrity," he said.

Turkey's Foreign Minister Ahmet Davutoglu said in Ankara on Tuesday that the surface-to-air missiles were "a precautionary measure, for defence in particular."

Originally used as an anti-aircraft missile, Patriots today are used to defend airspace by detecting and destroying incoming missiles and were made famous during the 1991 Gulf War as a defence from Scuds fired on Israel and Saudi Arabia from Saddam Hussein's Iraq.

Turkey's border villages have been hit by artillery fire from Syria as forces loyal to Damascus battle rebels seeking to oust President Bashar al-Assad's regime.

"It is the very mission of NATO to supply the security of its members, when one of them is threatened by this level of border violations and faced with even further risks, like ballistic missiles," Davutoglu said.

Germany and The Netherlands are the two main European nations that possess the medium-range missiles made by US group Raytheon and Rasmussen said it was up to "individual NATO countries that have available Patriots... to decide if they can provide them for deployment in Turkey and for how long."

German Defence Minister Thomas de Maiziere told German parliament on Wednesday that he would seek parliamentary approval for a military operation in Turkey by mid-December, after Ankara requested NATO help.

The Dutch foreign ministry said the request was under consideration and that "solidarity between allies would be an important factor" in its decision to deploy Patriots or not.

The United States said it was "favorably disposed" towards Turkey's request.

"We obviously... take the security of our NATO ally, Turkey, very seriously and we would be favorably disposed to this," State Department deputy spokesman Mark Toner said.

NATO deployed Patriot missiles in Turkey during the 1991 Gulf war and in 2003 during the Iraqi conflict.

Rasmussen said earlier this week that "the situation on the Syria-Turkey border is of great concern."

"We have all the plans ready to defend and protect Turkey if needed. The plans will be adjusted if necessary to ensure effective protection of Turkey," he said during talks with EU ministers on Monday.

Rasmussen said there was currently no question of imposing a no-fly zone with the back-up of the Patriot missiles.