US Defence Secretary Leon Panetta says the situation in Syria appears to be “spinning out of control.”
He was reacting to Wednesday’s deadly bombing that killed several senior members of President Bashar al-Assad’s inner circle.
Panetta, who met his British counterpart at the Pentagon, said the attack increased the urgency for tougher action from the United Nations.
“It is more essential than ever that the United States and the international community continue to work together through the United Nations, through whatever possible vehicles we have, to bring additional pressure on Assad to step down,” he said.
Britain and Germany also reiterated calls for the latest Chapter 7 resolution on Syria to be approved by the UN Security Council.
It authorises the extension of the UN observer mission and could lead to full-scale international military intervention.
German Chancellor Angela Merkel called for “all countries in the international community to participate so that we end the violation of human rights, but also so the political process can move ahead.”
Russia is against the use of force and wants to hold to the recent Geneva agreement calling for a transitional Syrian government which may include members of the current regime.
UN diplomats hope they can persuade Russia and China to accept tougher sanctions.
Wednesday’s Security Council vote on the resolution was delayed for 24 hours after calls from Kofi Annan, the international peace envoy to Syria.