Syrian government forces have fired Scud missiles at insurgents in recent days, escalating the 2-year-old conflict against rebels seeking to overthrow the regime, U.S. officials said Wednesday.

Speaking on condition of anonymity, two officials said forces of President Bashar Assad have fired the missiles from the Damascus area into northern Syria. These officials asked not to be named because they weren't authorized to discuss the matter publicly.

News of the missiles came on the same day that more than 100 countries, including the United States, recognized a new Syrian opposition coalition. That has further isolated Assad's regime and opened a way for greater humanitarian assistance to the forces battling to oust him.

One official said there was no indication that chemical weapons were aboard the missiles. Officials have said over the past week that they feared rebel advances were prompting Assad to consider using chemical weapons.

This official estimated that the number of Scuds fired was more than a half dozen, confirming details first reported by The New York Times.

State Department spokeswoman Victoria Nuland said Assad has fired missiles, but wouldn't specify what kind.

"As the regime becomes more and more desperate, we see it resorting to increased lethality and more vicious weapons moving forward and we have in recent days seen missiles deployed," she said.

White House press secretary Jay Carney, speaking to reporters, said he could not confirm the report, but said if true it would be a sign of desperation.

"The idea that the Syrian regime would launch missiles, within its borders, at its own people, is stunning, desperate and a completely disproportionate military escalation," Carney said.

The new development happened as officials planned an international conference to further assist opposition to Assad.

"This is the usual pattern of behavior that whenever there is an important decision that is anti-Assad taken by the international community, the Assad regime escalates the degree of violence to show its degree of displeasure," said Murhaf Jouejati, a specialist on Syrian affairs at the National Defense University. "Like saying, 'Oh, yeah? I'll show you!' "