U.S. troops have started to arrive in Turkey to man Patriot missiles meant to protect the NATO ally from potential Syrian warheads, the U.S. military said Friday.

The United States, Germany and the Netherlands are each deploying two batteries of the U.S.-built defense system to boost ally Turkey's air defenses against any spillover from Syria's nearly 2-year civil war. The Patriot systems are expected to become operational later this month.

The Stuttgart, Germany-based U.S. European Command said in a statement that U.S. personnel and equipment had started arriving at Turkey's southern Incirlik Air Base. Some 400 personnel and equipment from the U.S. military's Fort Sill, Oklahoma-based 3rd Battalion were to be airlifted to Turkey over the coming days, while additional equipment was expected to reach Turkey by sea later in January, the Command said.

NATO endorsed Turkey's request for the Patriots on Nov. 30 after several Syrian shells landed on Turkish territory.

Last month, NATO said the Syrian military has continued to fire Scud-type missiles, although none had hit Turkish territory, and said the alliance was justified in deploying the anti-missile systems in Turkey. Ankara is supporting the Syrian opposition and rebels and is providing shelter to Syrian refugees.

More than 1,000 American, German and Dutch troops are to be based in Turkey to operate the batteries. NATO said the Americans will be based at Gaziantep, 31 miles north of Syria. The Germans will be based at Kahramanmaras, located about 60 miles north of the Syrian border; the Dutch at Adana, about 66 miles west of the border.

Navy Vice Adm. Charles Martoglio, the Command's deputy chief, reiterated that the Patriots' deployment is for defensive purposes only and would not support a no-fly zone "or any offensive operation," in Syria, according to the Command's statement.

"Turkey is an important NATO ally and we welcome the opportunity to support the Turkish government's request in accordance with the NATO standing defense plan," it quoted Martoglio as saying.

Syria is reported to have an array of artillery rockets, as well as medium-range missiles -- some capable of carrying chemical warheads. These include Soviet-built SS-21 Scarabs and Scud-B missiles, originally designed to deliver nuclear warheads.

Last month, a top military commander from Iran -- a key Syrian ally -- warned Turkey against stationing the NATO systems on its territory, saying such a move risks conflict with Syria.