Geneva - The UN's special envoy on Syria has asked governments with influence to "twist arms" to halt the escalating violence in the country, his spokesperson said on Tuesday.
Ahmad Fawzi said former UN Secretary-General Kofi Annan is also working to convene a diplomatic meeting soon to discuss the situation in Syria amid worsening fighting between government troops and opposition forces.
"It is totally unacceptable and it must stop, and that is why Annan has invited governments with influence to raise the bar to another level, to the highest level possible, and twist arms if necessary, to get the parties to implement the plan," Fawzi told reporters in Geneva.
He didn't specify the countries that might be able to pressure the government of President Bashar al-Assad into halting its onslaught against the opposition, but Russia, China and Iran are considered Syria's closest and strongest allies.
Fawzi said the UN mission in Syria has observed heavy fighting in Rastan and Talbiseh, north of Homs, in which artillery, mortars and helicopters were used.
"They also reported that the Free Syrian Army had captured Syrian army soldiers," he added. "They reported a large number of civilians including women and children trapped inside Khaldiyeh in the city centre and they are trying to mediate their evacuation."
"The stronger party should send a strong signal in good faith and stop the violence, and the stronger party in this case is clearly the government of Syria," he said.
Fawzi said the escalating violence mirrors the spike in fighting that occurred shortly before a ceasefire plan was agreed in April, and the increase in sectarian tension is already spreading to neighbouring Lebanon.
"The longer this violence continues the more dangerous it becomes not only for the country and the Syrian people but the region," he said. "It's dangerous and the red light is flashing."
The use of helicopters by government forces - a clear breach of the ceasefire - has been documented by the UN observers for the first time, said Fawzi.
"A ceasefire is a ceasefire, whether it's from the air or from the ground," he said.
Diplomats have discussed the possibility of holding a meeting of all the parties in a neutral venue, to attempt to restore the faltering truce and implement the Annan peace plan.
"We hope that this contact group meeting will take place soon, but a venue and a time and a list of participants has yet to come together," said Fawzi.