Al Qaeda's presence in Syria has grown during the past year of revolt and instability there, leaving U.S. intelligence officials concerned that the terrorist group could plunder stockpiles of chemical and conventional weapons.

U.S. Ambassador to the United Nations Susan Rice warned Syria on Thursday that the regime will be held accountable if its large stockpiles of chemical weapons are not secured.

She also blasted Russia and China for blocking another United States-backed resolution by the U.N. Security Council that would have threatened stringent sanctions in an effort to curb the bloodshed that has already cost 17,000 lives since the uprising began last year.

"As the situation deteriorates, the potential that this regime could consider using chemical weapons against its own people should be a concern for us all," Rice told the U.N. members.

A U.S. official with knowledge of the ongoing crisis in Syria said there is evidence that a number of small al Qaeda factions have been operating in Syria.

"Al Qaeda's attempt to exploit the situation in Syria is yet another reason it would be beneficial to bring this conflict to a close so the Syrian people can begin the transition from the regime to a more stable nation," the official said.

Evidence shows the terrorist organization has been conducting its own operations, apart from the opposition groups that threaten to topple the government of President Bashar al-Assad.

"Their violent actions are not representative of the wider struggle to remove the Assad regime from power," the official said.

American intelligence officials aren't the only ones concerned that al Qaeda will gain access to Syria's chemical stockpiles.

On Wednesday, Jordan's King Abdullah told CNN that his intelligence agencies have information that "there is a presence of al Qaeda in certain regions inside Syria" and that they have been there for some time.

Abdullah said one of the worst-case scenarios "would be if some of those chemical stockpiles were to fall into unfriendly hands."

Syrian activists who've spoken to The Washington Examiner say there is growing evidence that the weapons are not secured and that the international community should be very concerned that some of them will be taken.

Sen. Lindsey Graham, R-S.C., told FOX News on Thursday that the U.S. should take an active leadership role to help the Syrian opposition.

"We should be with them in their darkest hour," Graham said, noting that if we abandon them now we will never gain their trust in the future. He said the U.S. "should not be covert but overt" and aid the rebels with arms and establish a no-fly zone.

Sara A. Carter is The Washington Examiner's national security correspondent. She can be reached at