International efforts to organize a peace conference designed to end the war in Syria gathered pace as the spiraling death toll and reports of atrocities by both sides raised alarm.
US Secretary of State John Kerry urged Syrian President Bashar al-Assad not to squander the opportunity to come to the table for negotiations, insisting "enormous plans are being laid" for what has been dubbed Geneva II.
And, in a possible sign of progress, Russian Foreign Minister Sergei Lavrov had also told the US chief diplomat that Assad had "already given him the names of people who will negotiate," Kerry said.
Last week in Moscow, Kerry and Lavrov announced plans for a new conference aimed at mapping a path towards a political transition in Syria and ending the bloody conflict now in its third year.
The two top diplomats were to meet for the second time in a week late Tuesday on the sidelines of talks on the Arctic in Sweden, as they grope for a solution based on a deal agreed in June last year in Geneva.
Exactly who will attend the conference, where it will be held and when, has yet to be determined, State Department spokesman Patrick Ventrell said.
There has been a flurry of diplomatic activity since the Moscow talks, with foreign ministers beating a path to the Russian capital to discuss the conflict in which an estimated 94,000 people have now died.
But Syrian Information Minister Omran al-Zohbi told the Hezbollah's Al-Manar television that Damascus wanted more details of the proposal before deciding whether to attend, saying Assad's departure was not up for discussion.
"We will not allow anyone to impose conditions on us... that affect the principle of sovereignty," he said.
Diplomats anticipate that the conference could now be held in early June, possibly in Geneva where the first talks were hosted.
Kerry also spoke Tuesday with the chief of staff of rebel Free Syrian Army General Salim Idris, whom her said is "committed to this negotiation process."
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Israeli Prime Minister Benjamin Netanyahu met Russian President Vladimir Putin on Tuesday to warn Moscow, which has stood by its traditional ally even while promoting the idea of talks, against sending arms to Syria.
In concluding remarks following talks at the Russian strongman's Black Sea residence in Sochi, the two leaders gave little away.
But Putin's official spokesman Dmitry Peskov confirmed that Israel had raised the issue and that Russia defended the arms deliveries.
"The issue was raised. The Russian Federation presented its arguments, which are well known," Russia's Interfax news agency quoted Peskov as saying.
Russia's position "was heard," Peskov added, without providing further details except to say that the meeting went "well".
Israel wants Russia to halt supplies of S-300 ground-to-air missiles that could severely complicate any future air attacks of the sort Israel has already carried out against the Syrian regime.
Netanyahu did not mention the sensitive weapons issue in public but Putin warned against any destabilizing moves in the Middle East, days after the latest Israeli strikes.
"In this crucial period, it is especially important to avoid any moves that can shake the situation," Putin said in televised remarks.
Jordan's foreign ministry said on Tuesday that Amman would host a meeting of the largely anti-Assad "Friends of Syria" group of Western and Arab states that is likely to discuss the conference.
The latest push to try to find an end to the slaughter in Syria comes as the war is continuing to intensify and amid reports that the Assad regime is starting to win back territory.
The Syrian Observatory for Human Rights said earlier Tuesday that at least 94,000 people had now been killed in more than two years conflict, increasing its previous estimated toll.
Syria has branded the watchdog a rebel front and there have been reports anti-regime fighters have also carried out abuses, most recently following a video in which a guerrilla is shown cutting out the heart of a regime soldier.