The West warned of more pressure on Syria if a crackdown against pro-democracy protests continues, hours after tanks stormed a city in the south, cradle of an uprising against Baathist rule.
U.S. Secretary of State Hillary Clinton said that both the European Union and the United States -- which have already slapped sanctions on a number of senior Syrian officials but not on President Bashar al-Assad -- were planning more steps.
"We will be taking additional steps in the days ahead," Clinton said, saying she agreed with EU foreign policy chief Catherine Ashton, who told reporters that the time for Syria to make changes was now.
Rights activists say a crackdown to crush a two-month wave of protests against Assad has killed at least 700 civilians.
Syrian tanks moved into a southern city on the Hauran Plain on May 17 after encircling it for three weeks, activists said.
Soldiers fired machine guns as tanks and armored personnel carriers entered Nawa, a city of 80,000 people 60 kilometers north of the town of Daraa, according to activists from the region.