As street fighting raged near the Syrian capital, a diplomatic battle loomed in the United Nations where the Arab League, backed by the West, wants the Security Council to act on an Arab peace plan that would call for President Bashar al-Assad to leave power.

The fighting on Monday subsided by nightfall as members of the anti-Assad Free Syrian Army (FSA) pulled out to the edges of the capital's suburbs, activists said by telephone, adding they believed 19 civilians and six FSA members had been killed.

Nabil Elaraby, the secretary-general of the Arab League, and Hamad bin Jassim Al Thani, the Qatari prime minister, meanwhile held talks with diplomats ahead of Tuesday's Security Council meeting on Syria.

Hillary Clinton, the US secretary of state, has said that she would travel to the UN for the meeting to "send a clear message of support to the Syrian people: we stand with you".

France, the UK, and Portugal are sending their foreign ministers to take part in the meeting.

A vote on the resolution drafted by Europeans and Arabs could come before the end of the week, diplomats say.

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Earlier, Russia, a veto-wielding Security Council member and one of Syria's few allies, said Assad's government had agreed to talks in Moscow to end the crisis, but a major opposition body rejected any dialogue with him, demanding he step down.

Russia, which has resisted Western calls to back UN sanctions against Damascus, had suggested to the government and the opposition that they should meet in the Russian capital for "informal contacts" without any preconditions.

"Our offer has already received a positive response from the Syrian authorities," Russia's foreign ministry said on Monday.

The head of the opposition Syrian National Council said that the opposition rejected all such talks with Damascus until Assad steps down.

"The resignation of Assad is the condition for any negotiation on the transition to a democratic government in Syria," Burhan Ghalioun told the AFP news agency.

Russia continues to block a draft UN Security Council resolution calling for a transfer of power in Syria, where it maintains a naval base at Tartous, near Latakia.

Call for action

The White House said countries needed to accept that Assad's rule was doomed, and stop shielding him in the Security Council.

"It is important that the Security Council take action," White House spokesman Jay Carney said. "We believe that the Security Council should not permit the Assad regime to assault the Syrian people while it rejects the Arab League's proposal for a political solution."

"As governments make decisions about where they stand on this issue and what further steps need to be taken with regards to the brutality of the Assad regime, it is important to calculate into your considerations the fact that he will go," Carney said. "The regime has lost control of the country and will eventually fall."

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Al Jazeera's Kristen Saloomey, reporting from the United Nations in New York, said that French diplomats are claiming that the resolution now has a majority of votes in the Security Council.

"All diplomatic muscles are being flexed here in New York in an attempt to win support for a resolution that is put forward by Morocco in the Security Council... But it comes down to China and Russia who have both expressed concern over the resolution."

The diplomatic moves came at a time when, according to activists, the clashes between the opposition and security forces have become deadlier with at least 160 people killed in the past two days.

Fierce street battles were reported in many other suburbs of Damascus, where security forces were said to have pushed rebel fighters back from their positions in Douma, Saqba and Hamuriyeh.

An activist named Kamal, speaking to the Reuters news agency by telephone from the Al-Ghouta area on the eastern edge of the capital, said that security forces had re-occupied the suburbs.

"The Free Syrian Army has made a tactical withdrawal. Regime forces have re-occupied the suburbs and started making house-to-house arrests," he said. A spokesman for the Free Syrian Army appeared to confirm that account.

Gunbattles were also reported in the towns of Deraa and Bab Amr. 

Pipeline attacked

Meanwhile, state media said "terrorists" had blown up a gas pipeline in the central province of Homs near the border with Lebanon, causing a leak of about 460,000 cubic metres of gas.

Al Jazeera's Anita McNaught, reporting from neighbouring Turkey, said this was not the first attack on pipelines in Syria.

"There have been at least five previous attacks since the start of the uprising. Damaging infrastructure is very much part of the strategy of the opposition forces. [...] It seems everything is in play now, perhaps even for either side."

Source: Al Jazeera and agencies