Geneva: US Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov will meet in Geneva on Friday for high-level peace talks on Syria, with Washington warning its patience is wearing thin.
The top diplomats from the two powers, which support opposite sides in the five-year conflict, will meet in the Swiss city to push for a peace agreement, Russia said.
Washington later confirmed Kerry was leaving for face-to-face talks with Lavrov.
The diplomatic news came after the US pressed Russia on Thursday for a "true cessation of hostilities" against a backdrop of continued military turmoil.
Coalition-backed forces were continuing to push the Islamic State group away from the Turkish border, an Islamist rebel leader died in a bombing attack and pro-regime forces made major gains on the outskirts of the ravaged city of Aleppo.
The talks "will focus on reducing violence, expanding humanitarian assistance for the Syrian people, and moving toward a political solution needed to end the civil war," State Department spokesman John Kirby said in a statement.
US Defense Secretary Ash Carter told BBC radio that there was "quite a long way to go" before a final peace deal could be struck.
He called for "a true cessation of hostilities -- not what you`ve seen, which is a partial cessation of hostilities," adding: "Our patience is not unlimited."
Both sides have agreed that a deal must involve a durable ceasefire, humanitarian access to conflict-wracked areas and a resumption of peace talks.
Amid a flurry of diplomatic efforts, Turkish President Recep Tayyip Erdogan and Russian counterpart Vladimir Putin agreed to intensify efforts for a ceasefire "as soon as possible" in Aleppo, the Turkish news agency Anadolu reported.
Moscow backs the government of Syrian President Bashar al-Assad, while Ankara supports the opposition seeking his ouster.
US President Barack Obama earlier held talks with Putin on the sidelines of the G20 summit in China but the two failed to bridge their differences.
Lavrov suggested that problems in another part of the world -- namely, US sanctions against Russia over the Ukraine crisis -- may be hampering efforts between the former Cold War rivals to resolve "regional conflicts," a reference to the Syrian war.
And Carter noted: "We have our differences, serious differences, with Russia elsewhere, especially here in Europe with Ukraine."Fighting in the complex war continued to claim lives, with Turkish shelling over the border into Syria killing six Kurdish fighters aligned with US forces on Thursday.
Syrian rebels supported by Turkish and coalition air strikes pushed further west into areas held by the Islamic State group in northern Syria.
The top military commander of the Army of Conquest, the largest Syrian rebel alliance, was killed in an air strike during a meeting of the leaders of the anti-government group, Islamist sources said Thursday.
The former Al-Nusra Front, renamed Fateh al-Sham Front, announced on Twitter "the martyrdom" of commander Abu Omar Sarakeb.
Pro-regime forces meanwhile overran a strategically important district on the southern outskirts of Aleppo, rolling back nearly every gain from a major month-long rebel offensive there, the Syrian Observatory for Human Rights said Thursday.
The government advance further seals off Aleppo`s opposition-held eastern districts. Regime forces backed by the Russian air force have completely encircled opposition-held neighbourhoods.
"Rebels are now back to square one, under an even more ruthless siege," Rami Abdel Rahman, head of the observatory, told AFP.
Shops in the city`s east have been struggling since Sunday to secure goods and prices are skyrocketing.
"The price of a kilo of meat rose from 3,000 pounds ($6) to 6,000," complained Ahmad, a father of three, in the Bustan al-Qasr district, ravaged by air strikes.
In London on Wednesday, the Syria opposition, under pressure, fleshed out a proposal for a transition to democracy without Assad after a six-month negotiating phase with the regime.
The opposition hopes new talks would result in an 18-month transition that would see Syria governed by an interim body made up of opposition figures, current government representatives and members of civil society, according to a 25-page blueprint.
The Syrian war -- which began as a pro-democracy revolt in 2011 but morphed into a multi-front conflict after the regime unleashed a crackdown -- has killed more than 290,000 people and forced more than half the population to flee their homes.
The Islamic State group has used the chaos to spread throughout the country and into Iraq. But it has lost ground in recent weeks.
Turkey said Wednesday that it favoured a joint operation with the US to oust the jihadists from their de facto capital of Raqa in northern Syria.
Erdogan said he had agreed with Obama to do "what is necessary."
