By Umit Bektas
HATAY, Turkey (Reuters) - Turkey has bolstered its defenses and deployed additional troops on its southeastern Syrian border in recent days as the United States tries to build international support for a military strike on Syria.
The reason for the additional security measures were not clear but Prime Minister Tayyip Erdogan has repeatedly said Turkey was ready to take part in any international coalition against Syria.
Ankara has been one of the biggest critics of President Bashar al-Assad's government and is openly supporting the rebels fighting to overthrow the Syrian leader.
Asked on Sunday what Turkey's role would be in a potential coalition against Syria, Erdogan said: "Whether it would be as an opposing force or supplying forces to provide logistical support, all this would be determined by circumstances."
The U.S. Congress is due to debate this week whether to authorize the use of force after President Barack Obama proposed limited strikes on Syria with the aim of punishing Assad's government for what Washington says was the use of chemical weapons on Syrian civilians.
Automated firing units using Stinger missiles for very short range air defenses have been set up on top of a high hill in Turkey overlooking the Mediterranean right on the Syrian border town of Yayladagi in Hatay province. The defense system's radar was active, a Reuters witness said.
Convoys of military vehicles have moved between bases near the southeastern border over the past week, carrying equipment and military personnel.
Neither the Turkish military, which rarely speaks to the media, nor the Ministry of Defense were available to comment on the additional measures.
Turkish daily Hurriyet also reported on Sunday that several Turkish fighter jets took off for a patrol flight from a southeastern air base near the Syrian border due to 'increased activity' in the area.
State news agency Anatolian reported on its website (www.aa.com.tr) similar deployments including tanks further east along the border in the Kilis and Gaziantep provinces.
Turkey has already been bolstering security along the 900 km (560 mile) frontier over the past year as the civil war in its southern neighbor has spilled onto its own soil.
It said late last month that it had already sent aid workers trained to identify and decontaminate chemical weapons victims to the Syrian border in preparation for another possible poison gas attack.
Turkey is sheltering more than a quarter of the 2 million Syrians who have fled the fighting since March 2011. The United Nations says more than 4 million people have been displaced inside the country. At least 100,000 people have been killed.
(Reporting by Umit Bektas,; Writing by Jonathon Burch and Humeyra Pamuk; editing by Anna Willard)