WASHINGTON: The US State Department on Monday voiced concern that escalating violence in Syria could spill over in the region, as the Pentagon said the conflict represented a security priority for Washington.

“We all fear the worst-case scenario: this devolving into a conflict that spills widely across the borders that is even further sectarian carnage,” State Department spokesman Patrick Ventrell told reporters.

“We are very concerned about that.” Ventrell again condemned the “despicable violence” seen in the village of Treimsa, and said Washington awaited further details from the UN mission in Syria about the killings in the central village.

Syria denied its troops carried out a massacre in Treimsa, while activists said dozens of people were slaughtered there last week by troops and pro-regime militiamen.

Pentagon spokesman George Little said the US navy would step up the pace of deploying an aircraft carrier group to the Middle East given the regional tensions, particularly in Syria and Iran.

“It’s no secret that the United States and our partners and our allies in the region face serious challenges, from a variety of sources,” Little said.

“Syria is obviously a top national security priority for the United States but I wouldn't get into whether or not these requirements as defined by Centcom are attached to the crisis in Syria.”Syria's military deployed armored vehicles near central Damascus for the first time on Monday as troops battled rebels around the capital in what activists said could be a turning point in the bloody 16-month uprising.

Russia, meanwhile, slammed as “blackmail” Western pressure to push for a UN Security Council resolution against Syria's regime and said it would be “unrealistic” for its ally President Bashar al-Assad to quit.

UN-Arab League envoy Kofi Annan is in Moscow for talks with top officials while UN chief Ban Ki-moon is due in Beijing on Tuesday, also on a mission to get support for tougher action on Syria.