"We closely monitor and we continue to closely monitor Syria's proliferation- sensitive materials and facilities," White House Press Secretary Jay Carney told reporters.
"As the opposition makes strategic advances and grows in strength, the Assad regime has been unable to halt the opposition's progress through conventional means, and we are concerned that an increasingly beleaguered regime, having found its escalation of violence through conventional means inadequate, might be considering the use of chemical weapons against the Syrian people," he said in response to a question.
US President Barack Obama has said that any use or proliferation of chemical weapons by the Syrian regime would cross a red line for the US, he said adding that the Assad regime must know that the world is watching and that they will be held accountable by the United States and the international community if they use chemical weapons or fail to meet their obligations to secure them.
"We continue to consult actively with Syria's neighbours, our friends in the international community and with the opposition to underscore our common concern about the security of these weapons and the Syrian government's absolute obligation to secure them," he said.
Responding to questions, Carney said the US believes the Assad regime in Syria remains in possession of chemical weapons.
"But as the regime has lost all legitimacy to lead Syria and the opposition grows in strength, our concern about the regime's intentions regarding its chemicals weapons stockpiles has increased," he said.
"The (US) president made clear that the use of weapons was a red line. We are monitoring the situation in Syria closely, and we are monitoring the regime's chemical weapons stockpiles. I'm not going to get into intelligence matters. We believe that with the regime's grip on power loosening, with its failure to put down the opposition through conventional means, we have an increased concern about the possibility of the regime taking the desperate act of using its chemical weapons," the White House Press Secretary said.
The US, he said, is consulting its allies and international partners as well as the Syrian opposition about this."There no doubt that we have an increased concern about this," he said, adding that the US is preparing its contingency planning.