Russian Foreign Minister Sergei Lavrov Tuesday pressed Syrian opposition leaders to open talks with the regime to stop the bloodshed after "constructive" talks with US Secretary of State John Kerry.
After the nearly two-hour meeting in Berlin, Lavrov called on the opposition to "declare itself in favour of dialogue" when it meets various Western leaders, including Kerry, at crunch talks in Rome on Thursday.
As diplomatic efforts intensified to end the conflict that has claimed 70,000 lives since it began in March 2011, fierce clashes erupted around the historic Umayyad Mosque in Syria's second city Aleppo.
And the humanitarian situation continued to worsen, with a record 150,000 people this month fleeing the fighting, according to the UN's top political official.
Lavrov said his Berlin talks with Kerry were "constructive", according to the Interfax news agency.
He added that representatives of the Syrian regime had "assured" Moscow that they "both have a negotiating team and are ready to start dialogue as soon as possible."
He called on the opposition also to name a negotiating team.
Meanwhile, State Department spokeswoman Victoria Nuland told reporters the two ministers had had a "really serious and hardworking session."
Nuland said the "bulk" of their discussions on foreign affairs "focused on Syria and how we can work together to implement the Geneva agreement", which remains hazy on whether Assad needs to step down before talks can begin.
Before the talks, Kerry stressed his personal relationship with Lavrov, voicing confidence the two could find "common ground."
Kerry, on an 11-day tour of Europe and the Middle East, his first foreign trip since taking over the office, earlier told an event in Berlin with German youngsters that he and Lavrov had a "good relationship".
Moscow and Washington have differences over Syria -- Russia is one of the few big powers to maintain ties with Assad's regime and, with China, has vetoed UN Security Council resolutions that would have imposed sanctions on Damascus.
But the US has recently toned down its criticism of Moscow's perceived intransigence over Syria.
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"We've been absolutely clear that there needs to be a political transition, and we felt that Russia could play a key role in convincing the regime... that there needs to be that political transition," a State Department official told reporters.
Ahead of the talks, Lavrov had blasted what he termed "extremists" that he said were blocking efforts at dialogue between rebels and regime.
"It seems that extremists who bet on an armed solution to the Syrian problem have prevailed in the ranks of the opposition at this time, including the so-called (Syrian) National Coalition, blocking all initiatives that could lead to the start of dialogue," he said.
There was "an increasing understanding of the need to influence both the government and especially the opposition" to stop them putting forward "unrealistic demands" before starting talks, he insisted.
"During our latest phone contact it seemed to me that he (John Kerry) understands the acuteness of the situation," he added.
-- The killing must stop --
Syrian Foreign Minister Walid al-Muallem had said in Moscow on Monday that the authorities in Damascus were ready to talk to armed rebels, the first time a senior official of the Assad regime had made such a proposal.
But the rebel Free Syrian Army's chief of staff Selim Idriss said that before any dialogue could begin, Assad's regime must fall, among other pre-conditions.
"I am not going to sit down with him or with any other member of his clique before all the killing stops, or before the army withdraws from the cities," he told pan-Arab broadcaster Al-Arabiya.
After initially threatening to boycott talks in Rome, Syrian National Coalition chief Ahmed Moaz al-Khatib said his group would attend after Kerry and British Foreign Secretary William Hague "promised specific aid to alleviate the suffering of our people".
Speaking after meeting Hague in London on Monday, Kerry told the Syrian opposition that "we are not coming to Rome simply to talk. We are coming to Rome to make a decision on next steps."
The trip sees Kerry, the son of a diplomat, back on familiar ground. He spent part of his childhood in Berlin and has family in France, where he arrived late Tuesday for the next leg of his tour.
Kerry also met German Chancellor Angela Merkel and standing next to her reminisced in a statement to reporters how he had cycled through Berlin past the then-destroyed Reichstag in his youth.
He was due next in Paris, before visiting Italy, Turkey, Egypt, Saudi Arabia, the United Arab Emirates and Qatar.