Syria's chemical weapons could be used at "a moment's notice" and the international community should not accept any assurances from Syrian officials that they will not be used, U.S. House Intelligence Committee Chairman Mike Rogers said on Wednesday.

U.S. and other Western officials recently issued sharp warnings to Syrian President Bashar Assad not to deploy chemical weapons. Syria called those warnings a "pretext for intervention" in the civil war.

Rogers, a Republican, told Reuters in an interview that the Syrian government's activities related to chemical weapons were a shift in posture and a major concern.

"I believe that they have put elements of their chemical weapons program in a condition of which they could be used at a moment's notice, which is very different from before," Rogers said.

"And some notion that they have promised not to use them, I don't think the international community ... should take that on face value," he said.

"This is a regime that's getting more desperate by the day. They have affirmatively put elements of their chemical weapon program in a position for use. That is something that we should all be concerned about."

His comments came amid reports that Assad's forces had fired Soviet-era Scud ballistic missiles against rebels in a significant escalation of the nearly two-year-old conflict that has already killed more than 40,000 civilians.

Rogers said more information was needed before he could say for sure whether the Scuds had been used.

"Some of the sourcing I've seen on the material just doesn't make me feel comfortable. We've seen a lot of mistakes based on social media, we're going to need more than that," he said.

But reports about use of Scud-style weapons and the changed posture on chemical weapons suggested desperation on the part of Assad's government, Rogers said.

But he added: "It would not be unusual for a regime that possesses some fairly sophisticated weapons systems in these last, I argue days and months, or days and weeks, of a pretty desperate regime to use the weapons at its disposal.

"So Scuds, and I make the next leap of chemical weapons, I think is of real concern."

Rogers has just returned from a visit to Bahrain and Saudi Arabia where he discussed Syria and other security issues with officials. Arab League officials want to see the United States step up its role on Syria, he said, adding that he was not referring to military action.

"The United States has a unique capability to deal with these," Rogers said, referring to Syria's chemical weapons. He would not describe the capability.

"I sensed a real frustration from our Arab League partners, frustration with the United States. I believe that we need to step up our role, and I am not talking about military, I'm just talking about U.S. influence and leadership and bringing unique capabilities that only the United States has to the table in these discussions," Rogers said.

"And again that doesn't mean boots on the ground. It does mean that we have unique capabilities that we should at least offer as a part of the discussion of how we prevent the use of these chemical weapons and the sheer humanitarian crisis in the region that I think would be created by their use."