UN Secretary-General Ban Ki-Moon has urged Syria's regime against using its stockpile of chemical weapons, warning of "huge consequences" if President Bashar Assad resorts to such weapons of mass destruction.
Mr Ban also suggested that he would not favour an asylum deal for the Syrian leader as a way to end the country's civil war and cautioned that the United Nations does not allow anyone "impunity".
"I again urge in the strongest possible terms that they must not consider using this kind of deadly weapons of mass destruction," Mr Ban said while attending a climate conference in Qatar. "I have warned that, if in any case this should be used, then there will be huge consequences. And they should be accountable," he said of the Syrian regime.
Syria is believed to have hundreds, if not thousands, of tons of chemical agents, including mustard gas, a blistering agent, and the more lethal nerve agents sarin and VX, experts say.
The Assad regime has said it would not use such weapons on its own people even if it had them. Syria is party to the 1925 Geneva Protocol banning chemical weapons in war.
US intelligence has seen signs that Syria is moving materials inside chemical weapons facilities recently, though it is unsure what the movement means. Nevertheless, US officials said the White House and its allies are weighing military options should they decide to secure Syria's chemical and biological weapons.
In Qatar, the UN chief was asked about the potential for an asylum deal that would remove Assad from power. The Syrian president vowed in an interview last month that he would never be forced into exile and that he would "live and die in Syria".
"Whoever commits (a) gross violation of human rights must be held accountable and should be brought to justice. This is a fundamental principle," Mr Ban said.
His warnings came as fighting around the Syrian capital, Damascus, was closing in on Assad's seat of power.
Clashes between rebels and regime troops have intensified in the suburbs around the city in recent weeks. The area has been a stronghold of predominantly Sunni Muslim rebels, who are fighting to topple Assad's regime, dominated by Alawites, an offshoot Shiite group.