"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 defense capabilities to defend the population and territory of Turkey."
Turkey stressed in its formal request the missile system, if approved, would be used only for defense and would not be part of any offensive operation or to enforce any no-fly zone if one is declared over Syria. Turkey shares a more than 500-mile border with Syria.
Rasmussen indicated the United States, Germany and the Netherlands had available Patriot missiles and it would be their decision whether to deploy them and for how long.
Patriot missiles previously were deployed in Turkey in 1991 and 2003.
He said the Patriot missile deployment "would contribute to the de-escalation of the crisis along NATO's south-eastern border. And would be a concrete demonstration of Alliance solidarity and resolve."
CNN said German likely would provide the U.S.-made missiles for Turkey, a NATO ally, if the deployment is approved by the NATO Council.