The UN has warned of an alarming escalation in violence in Syria and urged international powers to increase efforts to make its peace plan work.
A spokesman for Kofi Annan said the UN special envoy wanted a new conference to be held soon, but accepted the peace plan was the “only one on the table”.
A truce was agreed in April but the violence shows no sign of abating.
Intense shelling continues in Haffa in the north while activists say 10 people were killed in eastern Deir al-Zour.
Syrian troops are bombarding rebel positions in Haffa, and the US has warned that the Syrian government is planning another massacre there.
Separately, a UN report has accused Syrian troops of torturing children and using them as human shields to prevent attacks by opposition forces.
Mr Annan’s spokesman, Ahmad Fawzi, insisted the UN special envoy’s efforts were “coming together” and that “diplomacy had intensified”.
Mr Fawzi said it was hoped a meeting of an international contact group to discuss the status of the six-point peace plan for Syria would take place soon, although the date and list of participants had not been decided.
And he added: “The objective of creating this group is to give teeth to the plan, to convince the parties to implement the plan in its entirety – it’s not to create a new plan. This is the only plan on the table at the moment.”
Mr Fawzi said Mr Annan wanted international powers who had influence in Syria to “twist arms” to “put irrevocable pressure on the parties to implement the plan and stop the killing”.
Syrian ally Russia is coming under particular pressure to apply its influence on Damascus.
On Wednesday Russian Foreign Minister Sergei Lavrov will visit Iran to discuss Moscow’s call for a conference that would involve Tehran – a move strongly opposed by the US.
Meanwhile British Foreign Secretary William Hague, who is visiting Pakistan, said foreign military intervention was not being considered for Syria and that all efforts were being made for a peaceful transition.
“I think we should not think about it in terms of another Libya,” he said.
The diplomatic moves come against a backdrop of intense violence in Haffa, where troops have been besieging rebels for eight days.
Heavy tanks and helicopter gunships are being used, rebels said, with shells raining down.
One rebel commander from the Free Syrian Army told Reuters: “The situation is dire. Forget the weapons, people need medicine and food. As you know, we’re in a state of war in Syria. The army could enter Haffa in minutes if it wanted but it is trying to crush it instead.”
The rebels said they had brought civilians to the outskirts to try to evacuate them but those areas were also under fire.
US state department spokeswoman Victoria Nuland said there were fears the Syrian government “may be organising another massacre”, in Haffa, where the UN military observers in the country have been denied access.
The BBC’s Jim Muir in Beirut says Syrian state television has been playing recordings of what it says is an intercepted phone conversation between militants, with one of them ordering the rebels to carry out a massacre of civilians at Haffa, film it, and blame the government.
Earlier this month, activists said Syrian government forces killed 108 people in the region of Houla, in Homs province, and 78 people in the village of Qubair, in Hama province.
France said on Tuesday it also feared “new massacres” were being prepared in Syria.
In other reports of violence on Tuesday:
- Activists said the army had shelled a night-time protest in the eastern city of Deir al-Zour, killing 11 people
- In the central city of Homs, an activist told AFP the situation there was “horrific, murderous”, with 400 civilians trapped in a school in the Jourat al-Shiah district
- Syrian state television said two passenger buses were stopped outside Homs by “armed terrorists” and that an unspecified number of people were abducted
- Activists said Hreitan in the northern Aleppo province was subjected to violent army shelling
There is often no means of providing independent verification of reports within Syria.
‘Killed and maimed’
In its report on children and armed conflict the UN said children were being tortured in detention and slaughtered in massacres.
The UN special representative, Radhika Coomaraswamy, told the BBC her team had returned from Syria with “horrific” reports.
She said she had never seen a similar situation where children were not spared – and even targeted – in a conflict.
“Many former soldiers spoke about shooting into civilian areas, seeing children, young children being killed and maimed,” she said.
However, our correspondent says that although it is clear that children are being killed, maimed and abused, the report of them being used as human shields on tanks is not one that has surfaced before.
He says activists would have been the first to play this up, and if it had been common practice it would have been reported by those on the ground long ago.