Istanbul, Turkey (CNN) -- An early warning radar station that is part of NATO's controversial missile defense system in Europe is now operational in Turkey, a foreign ministry spokesman said Monday.
The station is located in the city of Malatya, about 400 miles southeast of the capital Ankara, and is manned by both Turkish and U.S. personnel, the spokesman said.
Turkey is one of five countries that have agreed to deploy parts of the U.S.-designed defense system. Portugal, Poland, Romania and Spain have also agreed to participate.
NATO asked Russia to participate in the system but negotiations have been deadlocked over Russia's demand for a legally binding treaty guaranteeing the shield would not be used as a deterrent to Moscow's own systems. The United States and its European allies have insisted the system is directed toward countering ballistic missile threats from such Middle East countries as Iran.
Iran -- Turkey's eastern neighbor -- has publicly objected to the NATO system. Ali Larijani, Iran's speaker of parliament, repeated his opposition to it during a visit to Turkey last week.
NATO Secretary-General Anders Fogh Rasmussen has said he hopes a political agreement with Moscow can be reached before a summit between NATO and Russia in Chicago this spring. That is when NATO is expected to declare an interim operational capability of the defense system.
The only Muslim-majority country in the NATO alliance, Turkey is a critical ally to the United States, both in the region and globally.
"The fact that they are willing to accept a defense radar system, I think it's important for us to work closely with Turkey at this critical time because they can be an important ally and an important influence on the direction in the Middle East," U.S. Defense Secretary Leon Panetta said last month during a visit to the Middle East.
CNN's Ivan Watson and Elise Labott contributed to this report.