But the stronger the radical groups become, the more the United States worries that the fighting -- not political efforts to find a solution -- will decide the outcome in Syria. As a result, Washington has been pushing the opposition to unite. That process is unfolding with the recent creation of the National Coalition for Syrian Revolutionary and Opposition Forces.

Early next week, Clinton will travel to Marrakesh, Morocco, for a meeting of the Friends of the Syrian People, a gathering of countries that support the political transition. The Obama administration, while providing, for now, non-lethal assistance, is expected to take the first steps toward officially recognizing the National Coalition at that meeting.

Clinton also reiterated Wednesday the strong U.S. position set out by President Barack Obama on Monday over any possible use by Syria of chemical weapons. She said the international community is sending a clear message to Damascus.

"Our concerns are that an increasingly desperate Assad regime might turn to chemical weapons or might lose control of them to one of the many groups that are now operating within Syria," she said.

"And so, as part of the absolute unity that we all have on this issue, we have sent an unmistakable message that this would cross a red line and those responsible would be held to account."

U.N. Secretary-General Ban Ki-moon said on a visit to Baghdad Thursday that he had expressed his "gravest concerns" to Syria's government over any use of chemical weapons and had written directly to al-Assad.

He warned that anyone responsible for the use of chemical weapons would face serious consequences.

Ban is to meet with the head of the Organization for the Prohibition of Chemical Weapons in Baghdad to discuss how it can work with the United Nations on the issue.

NATO foreign ministers agreed this week to a request by Turkey for Patriot missiles to be deployed along its border to bolster its air defenses against potential Syrian threats.

Errant Syrian artillery shells struck the Turkish border town of Akcakale and killed five Turkish civilians in October.

Early Thursday, the German Cabinet agreed to send Patriot missiles and up to 400 soldiers to Turkey to deter the Syrian civil war from spilling into the country. Germany's parliament will vote on the deployment next week, the foreign ministry said.

In addition to Germany, the United States and Netherlands, both of which have Patriot capabilities, have signaled they would be willing to contribute missiles.

"Any deployment will be defensive only. It will in no way support a no-fly zone or any offensive operation," the NATO statement said.

NATO's decision was made as the fears surfaced that the Assad regime might be preparing to use chemical weapons.

"The Syrian stockpiles of chemical weapons are a matter of great concern," NATO Secretary General Anders Fogh Rasmussen said.

"We know that Syria possesses missiles. We know they have chemical weapons and, of course, they also have to be included in our calculations," he said. "And this is also the reason why it is a matter of urgency to ensure effective defense and protection of our ally Turkey."

In the United States, Republican Sen. John McCain said Thursday that time may be running out.

"If true, these reports may mean that the United States and our allies are facing the prospect of an imminent use of weapons of mass destruction in Syria, and this may be the last warning we get," McCain said. "The time for talking about what to do may now be coming to a close and we may instead be left with an awful and very difficult decision."