The office recommended that the United Nations Security Council consider referring Syria to the International Criminal Court for prosecution. In New York, the Security Council met later on Thursday and discussed potential steps against Syria.

The United States and European members of the Security Council pressed for a resolution condemning Syria and were debating sanctions that could include an arms embargo, a freezing of assets and a ban on travel by the country’s leaders, diplomats there said. They would not say whether the Council would consider referring the matter to the international court, but did say that Council members expressed a desire to hold accountable those responsible for the violence. At the United Nations, Syria said the United States was trying to use the Security Council as an “instrument” to instigate further instability.

Even Russia, which has resisted punitive measures against Syria so far and appears likely to veto an embargo, has sounded increasingly frustrated with Mr. Assad’s government, which has ignored repeated calls to halt the violence, including those from countries like Turkey with which it had closer relations. While Mr. Assad told the United Nations secretary general, Ban Ki-moon, on Wednesday that the crackdown had in fact ended, activists within Syria said the violence continued unabated.

After Mr. Assad spoke on Wednesday, two people were reported killed in the city of Homs after a nighttime prayer, held only during the month of Ramadan, when Muslims fast from dawn to sunset; at least one more died in the city on Thursday when security forces opened fire on a small protest in the neighborhood of Baba Amr. Residents and activists also reported attacks and arrests in other cities, including Deir al-Zour, Hama and the capital, Damascus. “The killings and destruction haven’t stopped,” an activist in Homs, who would be identified only as Mohamad, said in a telephone interview on Thursday. “They haven’t withdrawn from the city. On the contrary, the number of security forces has increased and gunfire is heard every so often.”

In Washington, administration officials acknowledged that American sanctions alone would have little effect. “No outside power can or should impose this transition,” Secretary of State Hillary Rodham Clinton said at the State Department. “It is up to the Syrian people to choose their own leaders, in a democratic system based on the rule of law and dedicated to protecting the rights of all citizens, regardless of ethnicity, religion, sect or gender.”