US Secretary of State John Kerry and his Russian counterpart Sergey Lavrov are meeting in the Swiss city of Geneva to discuss a ceasefire deal for Syria.
During the snap meeting, the two diplomats will hold talks on how to put an end to fighting in the wartorn country and further humanitarian aid for the Syrian people, according to the US State Department.
"Their discussion follows recent conversations on Syria and will focus on reducing violence, expanding humanitarian assistance for the Syrian people, and moving towards a political solution needed to end the civil war," spokesman John Kirby said in a written statement.
The US and Russia have backed opposite sides in a war showing little sign of ending since its beginning in 2011.
Moscow is a leading supporter of the Syrian government led by President Bashar al-Assad, while Washington backs the rebels. Both powers have been fighting the common enemy the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group in Syria.
Al Jazeera's Jonah Hull, reporting from Geneva, said that the US and Russia have been trying hard in recent months to hammer out a ceasefire deal and pave the way for the UN-sponsored peace talks to start in Geneva.
"On Thursday, it did not even look like Kerry was coming to Geneva at all. The State Department said that the two sides were not close enough to warrant a meeting. It is not clear what changed after that," he said.
Senior US officials said Kerry would not have flown out to the high-level face-to-face talks with Lavrov unless he thought there was a chance of progress.
However, they warned there was no guarantee of a final agreement within the narrow window available before both men return home later on Friday.
"We have been taking issues off the table because we've reached an understanding on them. We continue to have some issues that remain outstanding and that we have been unable to close," an official was quoted as saying by the Reuters news agency.
"We cannot guarantee at this point that we are on the cusp of finishing," he said, adding that the remaining issues were highly technical and complicated.
Rami Khoury, a syndicated journalist and senior fellow at the American University of Beirut and Harvard University, told Al Jazeera that any agreement between Kerry and Lavrov would only relate to the implementation of a humanitarian pause, and "would not touch on any of the other critical issues where no progress has been made".
"Even a humanitarian pause - which everyone wants, especially the Syrian people - will not allow any significant movement towards a political resolution," he said.
"But both the Russians and the Americans feel obligated... they've got to do something to stop pictures of children choking on chlorine gas or being starved to death from appearing on television screens all over the world every day because it reflects directly on the super powers, as well as on the actors on the ground."
Aleppo key issue
Washington wants concrete steps from Russia to force its Syrian ally Assad to stop bombing his own people and to lift the siege of Aleppo, a key city near the Turkish border.
"We need to see a situation where it is clear within whatever is being agreed with the Russians that there will not be a siege of Aleppo," a senior US official quoted by the AFP news agency told reporters.
Pro-government forces have recently taken back a strategically important district on Aleppo's southern outskirts, rolling back nearly every gain from a major month-long rebel offensive there, the Syrian Observatory for Human Rights said on Thursday.
The government advance further seals off Aleppo's opposition-held eastern districts and government troops backed by the Russian air force have completely encircled opposition-held neighbourhoods.
The conflict has so far claimed an estimated 400,000 lives, according to the UN special envoy for the Syria crisis Staffan de Mistura. Millions of others have been displaced during the five years of war.
Source: Al Jazeera And Agencies