Russia, the only world power with close ties to the Syrian regime, urged President Bashar al-Assad on Friday to talk to the opposition as Moscow itself put out feelers that received a cold reception from the rebels.
The new pressure on Assad came as Moscow revved up its bid to save a tattered peace process by first hosting a top Damascus envoy and then planning for a meeting Saturday with Syria peace mediator Lakhdar Brahimi.
Russia also invited the head of the opposition National Coalition for talks in either Moscow or a regional capital -- the Kremlin's first contact with a group formed in November and recognised by the West as the sole legitimate representative of Syrians.
But Moscow still views Assad as the legitimate leader, and its outreach to the regime's opponents received a cool response from National Coalition chief Ahmed Moaz al-Khatib who rejected the invitation to Moscow, accusing Russia of interference.
"We have said frankly that we will not go to Moscow," Khatib told Al-Jazeera television.
"We want apologies from (Russian Foreign Minister) Sergei Lavrov," for "interfering" in Syrian affairs and for Moscow's refusal to condemn "massacres" committed by the regime, he said.
"They have to issue a clear condemnation of the regime's brutality and a clear call for the departure of President Bashar al-Assad, which is a condition for any negotiations."
If these conditions were met, talks could be held with the Russians "but only in an Arab country and if there is a clear agenda", he said.
The fast-paced but tricky diplomacy came as government air raids on the town of Al-Safira, south of second city Aleppo, killed 15 civilians, eight of them children, the Syrian Observatory for Human Rights said.
In Deir Ezzor province in the east, rebel fighters overran the Tanak oilfield east of the provincial capital, the Britain-based watchdog said.
Video footage posted on the Internet by activists showed the bloodied corpses of six soldiers they said were killed in the fighting. Its authenticity could not be verified.
The Observatory said three rebel fighters were also killed.
The rebels control a large swathe of territory in the east stretching from close to Deir Ezzor city to the Iraqi border.
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Nationwide, at least 153 people were killed in violence on Friday, 47 of them civilians, the Observatory said.
Lavrov said Russia still refused to back international calls on Assad to step down.
But the foreign minister made explicit that Russia wanted Assad to put all options on the table after 21 months of violence that have claimed more than 45,000 lives.
"We actively encouraged... the Syrian leadership to maximally put into action its declared readiness for dialogue with the opposition," Lavrov told reporters when asked about his meeting on Thursday with Syrian Deputy Foreign Minister Faisal Muqdad.
The West lacks direct access to Assad and needs Russia to convince him that his regime's days are numbered.
In recent weeks, Moscow appears to have distanced itself from the ruler of what was its last big ally in the Middle East. President Vladimir Putin has twice this month said that Moscow has no intention of propping up Assad.
"Russia has long realised that Assad has no future," said Carnegie Moscow Centre analyst Alexei Malashenko.
Moscow will be the focus of further diplomacy on Saturday when Russian officials hold talks with Brahimi.
The UN-Arab League envoy revealed on Thursday that he had been discussing the details of a transition government that had full powers and implemented "real change".
But Lavrov stressed that peace efforts were futile unless the West impressed on the armed opposition the need to engage in talks that left open the possibility of Assad staying on on an interim basis.
The United Nations said meanwhile that Secretary-General Ban Ki-moon will chair an international conference on January 30 to raise money for Syrian civilians caught up in the civil war.
"The international community must do more to alleviate the suffering of millions of people in Syria and the neighboring countries," Ban said, according to a statement from his spokesman, Martin Nesirky.
The conference was announced earlier this week by Kuwait's ruler, Sheikh Sabah al-Ahmad Al-Sabah, but it was not known that Ban would chair the gathering.