Turkey is expected to formally request on Monday that NATO missiles be placed on its border with Syria to defend against mortar rounds, Western defence officials said.
Only the United States, the Netherlands and Germany have the appropriate Patriot missile system available, and Germany would analyse such a request "with solidarity", German Defence Minister Thomas de Maiziere said.
"I expect that there will be a request from the Turkish government today to NATO to deploy Patriot missiles to the Turkish border," de Maiziere told reporters in Brussels, on the sidelines of a meeting of EU defence ministers.
NATO has not yet received a request but will consider it "as a matter of urgency", Secretary General Anders Fogh Rasmussen told reporters as he arrived at the meeting.
"Turkey can count on allied solidarity," he said, while emphasising that the missiles would only be to counter mortar rounds, not to enforce a no-fly zone over Syria.
"We are not speaking about a no-fly zone. If we are to deploy patriot missiles it would be a purely defensive measure to defend and protect Turkey."
The alliance has deployed Patriot surface-to-air missiles to Turkey twice before, once in 1991 and later in 2003, during both Gulf Wars. Those missiles were provided by the Netherlands.
De Maiziere said the German response would depend on the details of any request. "But if we have a deployment of Patriots on the Turkish border then this will happen with German soldiers."
Turkey is talking to NATO allies about how to shore up security on its 900-km (560-mile) frontier with Syria after mortar rounds fired from Syria landed inside its territory, increasing concerns about spillover from the civil war from its neighbour.
The Dutch defence minister said the Netherlands too was waiting for a Turkish request. "We did not receive a formal request yet," Jeanine Hennis-Plasschaert told reporters in Brussels. "We are waiting for a formal request."