UN-Arab League peace envoy Lakhdar Brahimi has said that Syria faces a choice between "hell or a political process", urging the international community to work tirelessly to bring about a political solution to the crisis.
"If the only alternative is hell or a political process, then all of us have to work continuously toward the political process," Brahimi said after talks with Russian Foreign Minister Sergei Lavrov in Moscow on Saturday.
He warned that Syria could turn into a failed state if action is not taken soon.
On his turn, Lavrov said that Syrian President Bashar al-Assad was insisting on staying in power and nothing could be done to persuade him to step down.
"Regarding Bashar al-Assad, he repeatedly said, both publically and in private... that he is not planning to leave, that he will remain in his post," Lavrov said alongside Brahimi.
"There is no possibility to change this position."
Lavrov said there is still a chance of finding a political solution to the conflict, even as he warned against "terrorist elements" operating within the trouble Middle Eastern nation.
"The confrontation is escalating. But we agree the chance for a political solution remains," Lavrov said, adding that he was "surprised" by the negative reaction of the Syrian opposition to an offer of talks in Moscow.
"Their refusal to have any dialogue with the government is a dead end position," Lavrov said.
Earlier in the day, the head of the Syria National Coalition told Al Jazeera that his group would not participate in the negotiations.
"We have said frankly that we will not go to Moscow," said Ahmed Moaz al-Khatib, demanding instead that Russia apologise for its pro-Assad policy.
Khatib said Russia should apologise for "interfering" in Syrian affairs, condemn "massacres" committed by the regime and issue a "clear call for the departure of President Bashar al-Assad".
The chief of the staff of the Supreme Military Council, Salim Idriss, also said the fighters would not accept anything that did not state in clear terms al-Assad's departure.
Fighting in Homs
As the meeting was in progress, forces loyal to al-Assad seized a district of the central city of Homs after a fierce assault that sparked a humanitarian crisis, a monitoring group said.
"The army launched an offensive several days ago on the neighbourhood of Deir Baalbeh with heavy bombing, and the fighting and attacks continued until the rebels withdrew," on Saturday, the Syrian Observatory for Human Rights said.
In-depth coverage of escalating violence across Syria
Elsewhere, the army also battered the rebel-controlled area around the Crac des Chevaliers crusader castle, a UNESCO listed world heritage site to the west of Homs.
In the north, fighting raged around Menagh military airport near Syria's second city of Aleppo, after rebels managed to penetrate the base on Thursday following a months-long siege, said the watchdog group.
Assad's forces targeted different parts of Aleppo city with rockets overnight, as clashes persisted. They also bombarded several areas across the same province, the group said.
Regime shellfire was also reported in the provinces of Hama in central Syria and southern Daraa, where a man was tortured to death soon after being arrested.
There were also clashes in the eastern region of Deir Ezzor.