The top U.S. military commander in Europe says several NATO countries are discussing plans for possible military action in Syria.
Admiral James Stavridis said any such military action would require a UN Security Council resolution and agreement among all 28 members of NATO.
Stavridis' remarks March 19 before the U.S. Senate Armed Services Committee come after Syria's government and rebels accused each other of launching a deadly chemical attack near the northern city of Aleppo.
Syria's state-run SANA news agency said 25 people were killed and dozens wounded in the alleged rebel attack on March 19.
UN Secretary-General Ban Ki-moon said the use of such weapons “would constitute an outrageous crime."
The World Health Organization said it was sending medical supplies to Aleppo, but could not verify if chemical weapons or some other toxin had been used there.
Other international organizations, including the Organization for the Prohibition of Chemical Weapons and the International Committee of the Red Cross said they had no independent information on the alleged chemical attack.
In Washington, White House spokesman Jay Carney said the United States has no evidence to back the Syrian government's claim that rebels used chemical weapons.
Carney said it is a serious concern for the United States that the Assad regime could use such weapons.
Russia, meanwhile, appeared to back the Syrian government's claim.
The Russian Foreign Ministry said "information coming from Damascus" on the use of chemical weapons by rebels was "extremely dangerous."
Based on AP and AFP reporting