Syria's government said the U.S. told it of plans to carry out airstrikes against Islamic State targets in Syrian territory, as the Obama administration opened up a new front in an expanding Middle East campaign.

The U.S. State Department immediately denied that it had given the regime of President Bashar al-Assad prior notification.

The claim underscored the delicate balancing act the U.S. and its allies face in forging ahead with their campaign against the extremist groups in a country mired in a more than three-year multi-sided civil war in which the adversaries are striving for political and military advantage. (More:U.S. Reports Significant Damage in Attacks on Islamic State, Khorasan)

Mr. Assad's government, which was excluded this month from the U.S.-led coalition against Islamic State and labeled illegitimate by Washington, appears to be trying to show that the U.S. reversed its position and is now coordinating with Damascus.

"We are witnessing the beginning of change in the U.S. position," said Bassam Abu Abdallah, director of the Damascus Center for Strategic Studies, which is close to the Syrian regime. "And in politics you have to deal with reality no matter how long you resist; there is a Syrian state that has persevered and there are institutions that one can communicate with."