U.S. Secretary of State Hillary Clinton says world powers must show the Syrian government that there are consequences for what she called a "brutal crackdown" on civilians.
Clinton says she discussed possible sanctions against Syria during a meeting with Italian Foreign Minister Franco Frattini in Rome on Thursday.
Rights groups say at least 560 civilians have been killed in Syria's crackdown on nationwide anti-government unrest.
Syria says it has started a gradual withdrawal of military forces from the city of Daraa, where there have been deadly clashes between security forces and anti-government protesters.
The state-run news agency SANA quoted a military official on Thursday as saying the army had completed its mission of detaining so-called "terrorist elements" in the southern city and restoring calm and stability.
Two witnesses leaving Daraa told the Reuters news agency that about 30 tanks on armored carriers had left the city heading north, but that army units remained at several entrances.
The news agency also quoted residents in Daraa saying at least six tanks were deployed near government installations and public squares, snipers were on rooftops, and security barriers were placed every 100 meters.
The Syrian government sent troops and tanks into Daraa when anti-government protests that began as calls for reform developed into demands for the ouster of President Bashar al-Assad.
On Wednesday, witnesses reported seeing military reinforcements in other cities including Rastan and Homs as well as outside of the capital, Damascus.
Syrian security forces have intensified their crackdown on opposition protesters, detaining more than 1,000 people in recent days as international condemnation of Assad's government widens.
Some information for this report was provided by Reuters.