Russian Foreign Minister Sergei Lavrov met the UN-Arab League peace envoy Lakhdar Brahimi in Moscow for talks that represented a final end-of-year bid to accelerate moves to find peace in Syria.
Brahimi bluntly stated that Syria was facing a choice between "hell or the political process", and said the world had to work tirelessly to bring about a diplomatic solution.
Lavrov said both he and Brahimi agreed there was a chance for a solution to the conflict that has lasted 21 months and claimed over 45 000 lives according to rights groups.
"The confrontation is escalating. But we agree the chance for a political solution remains," Lavrov said alongside Brahimi.
Commentators have in recent weeks detected a shift in Russia's tone on the conflict with Moscow appearing to acknowledge that Assad's chances of political survival were dwindling.
But Lavrov said that Assad was still insisting – including most recently to Brahimi on the envoy's latest trip to Damascus – that he would be staying in power.
"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.
"There is no possibility to change this position."
Brahimi gave a stark warning about the magnitude of the crisis in Syria and said it risked becoming even worse if fighting engulfs the capital Damascus which could exacerbate a refugee crisis.
"If the alternative is hell or the political process, we have all of us got to work ceaselessly for a political process," Brahimi said.
"The magnitude of the problem that exists now and the magnitude of the problem that exists tomorrow cannot be ignored," he added.
Russia 'interfering' in Syria
Brahimi's trip came amid a flurry of diplomatic activity in Moscow on the Syria conflict that this week also saw a rare visit by the Syrian deputy foreign minister as well as Egypt's top diplomat.
In contrast to Russia's past suspicion of the rebels battling the Assad regime, Deputy Foreign Minister Mikhail Bogdanov also said Thursday that Russia had made an offer of talks to the opposition Syria National Coalition.
However the head of the group – formed in November with the encouragement of the West – showed little enthusiasm for the idea, saying such talks could not take place in Moscow and demanding that Russia apologise for its past policy.
"We have said frankly that we will not go to Moscow," Ahmed Moaz al-Khatib told Al-Jazeera television.
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 Assad.
Lavrov said he was "surprised" by Khatib's reaction to the invitation and attacked the Syrian opposition for demanding "Assad's ouster as a prerequisite for everything else."
Russia has infuriated the West throughout the conflict by refusing to halt military cooperation with the Assad government and vetoing UN Security Council resolutions that would have sanctioned the regime.
The fast-paced diplomacy came as violence continued to rage on the ground with forces loyal to Assad seizing a district of the central city of Homs after a fierce assault that sparked a humanitarian crisis.
"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," said the Britain-based Syrian Observatory for Human Rights.
It said the day earlier that government air raids on the town of Al-Safira, south of second city Aleppo, killed 15 civilians, eight of them children.
With concerns intensifying about the humanitarian situation, UN chief Ban Ki-moon will chair an international conference on January 30 in Kuwait to raise money for Syrian civilians caught up in the conflict, the United Nations said.
The UN is calling for $1.5-billion to help through June nearly one million Syrian refugees and four million other Syrians affected by the conflict but who remain the country.
The UN refugees office registered 500 000 Syrian refugees and expects nearly a million more by June – figures that represent 4.4% of the pre-crisis population. – Sapa-AFP