British Minister for the Middle East Alistair Burt said his government was "deeply concerned" by what he said was "reprehensible violence" attributed to Syrian forces.
Burt said U.N. monitors in Syria have reported a steady presence of military forces in Syrian cities despite commitments made as part of an April 10 cease-fire.
Syria's official Syrian Arab News Agency reported Friday that nine people were killed in a suicide bombing in Damascus.
The bombing came a day after U.N. Secretary-General Ban Ki-moon said he was "gravely alarmed" by opposition reports of intense government shelling in Hama.
French officials said this week they'd consider a U.N. Security Council resolution authorizing the use of force in Syria. Burt called on Damascus to meet obligations outlined in a cease-fire brokered by former U.N. Secretary-General Kofi Annan. This, said Burt, includes political transition.
"If the regime does not do so and Annan cannot make progress we will return to the U.N. Security Council to discuss immediate and robust action," he said in a statement. "We continue to urge the opposition to adhere to the cease-fire and also to work with … Annan on a political transition."