US Secretary of State Hillary Clinton on Monday issued a "strong warning" to the regime of Bashar al-Assad over the potential use of chemical weapons against the Syrian people, AFP reports.
"This is a red line for the United States," Clinton said after meeting Czech Foreign Minister Karel Schwarzenberg.
"Once again we issue a very strong warning to the Assad regime that their behaviour is reprehensible. Their actions against their own people have been tragic," she added.
"I'm not going to telegraph in any specifics what we would do in the event of credible evidence that the Assad regime has resorted to using chemical weapons against their own people, but suffice it to say that we're certainly planning to take action if that eventuality were to occur," the top US diplomat stressed.
"There is no doubt that there is a line between the horrors that they [the Assad regime] have already inflicted on the Syrian people and moving to what would be an internationally condemned step of utilising chemical weapons," Clinton stressed, without providing further details on the nature of the planned action.
The warning came as the New York Times reported Monday that the Americans and Europeans had sent warnings via intermediaries to the Syrian regime after detecting movement of chemical weapons by the Syrian military in recent days.
"The activity we are seeing suggests some potential chemical weapon preparation," one US official told the daily, which added that the activity over the weekend has set off a flurry of emergency communications among the Western allies.
NATO is preparing to meet on Tuesday for two days of talks, with the brutal conflict in Syria set to top the agenda.
On Sunday, a senior US State Department official told reporters travelling with Clinton that Washington was "hopeful that NATO will be in a position to respond positively and agree to help Turkey bolster its air defences" by approving Ankara's request to deploy Patriot missiles on the border with Syria.
"If NATO takes a positive decision to do it... I think it would still probably be at least a matter of weeks," the official said, asking to remain anonymous, as Clinton arrived in the Czech Republic on the first stop of a five-day Europe trip.
The British-based Syrian Observatory for Human Rights says more than 41,000 people, including thousands of infants, children and women, have perished since the uprising against Assad's regime erupted in March 2011.