WASHINGTON (Reuters) - The United States is concerned by reports that Syria is massing troops near the border with Turkey, which could escalate the crisis in the region, and is discussing the issue with Turkish officials, U.S. Secretary of State Hillary Clinton said on Thursday.
Clinton said the reported move by Syria to surround and target the town of Khirbat al-Joz just 500 meters (yards) from the Turkish border marked a worrying new phase of Syria's attempt to quash anti-government protests.
"If true, that aggressive action will only exacerbate the already unstable refugee situation in Syria," Clinton said in an appearance with the visiting Filipino foreign minister.
"Unless the Syrian forces immediately end their attacks and their provocations that are not only now affecting their own citizens but (raising) the potential of border clashes, then we're going to see an escalation of conflict in the area," Clinton said.
Syria's moves have raised tensions with Turkey as President Bashar al-Assad increases the use of military force against a popular revolt.
Clinton said she had discussed the situation at length with Turkish Foreign Minister Ahmet Davutoglu and that President Barack Obama had also talked to Turkish Prime Minister Tayyip Erdogan.
"We are closely monitoring the situation in Syria and in neighboring countries," Clinton said.
"It is further example of the lengths to which President Assad's regime will go to repress the people of Syria rather than actually working in a collaborative way to try to resolve the legitimate concerns of the Syrian people."
The United States has steadily sharpened the tone of its rhetoric toward Assad, saying the Syrian leader is losing credibility and must either implement promised reforms or get out of the way.
Clinton said that by bringing the conflict so close to Turkey -- which in the 1990s had tense relations with Damascus over Syrian support for the Kurdish militant group PKK -- Assad was taking a dangerous step.
"This is a very worrisome development by the Syrians. They have to know what they're doing and they have to, I assume, know their own history because this is not the first time that they had a provocation that led the Turks to take action to protect their own interests," she said.
(Editing by Eric Walsh)