VIENNA (AP) — The United States, Russia and other regional and world powers considered a new plan Friday to set up a cease-fire in Syria within four to six months, followed by the formation of a transition government featuring both President Bashar Assad and opposition members, officials told The Associated Press.

Federica Mogherini, the European Union’s chief diplomat, said parties agreed to initiate a “U.N.-led” political process. But how long Assad could remain in power under a transition was still unclear.

The Western officials said the United States and its partners supported the timetable as a first phase toward ending the four-and-a-half year civil war that has killed more than 250,000 people and uprooted more than 11 million, leading to the growing terrorist threat of the Islamic State and sparking a refugee crisis throughout Europe. They said an agreement hadn’t yet been reached, but that the 19 nations meeting in Vienna were considering the idea.

The officials, who spoke on condition of anonymity because they weren’t authorized to speak publicly on the matter, said that a follow-up meeting was expected as early as next week, with top diplomats possibly returning to Austria’s capital.

The indications of diplomatic progress coincided with the U.S. preparing to announce that a small number of America special operations forces will be sent to northern Syria to work with local ground forces in the fight against Islamic State militants. It would mark the first time American troops would be deployed openly on the ground in the country.

As the day of discussions in Vienna got underway, U.S. Secretary of State John Kerry said he was hopeful of finding a path forward. The talks included Iran for the first time, making it the broadest gathering of nations yet to discuss Syria’s future. Another key supporter of Assad, Russia, was present, along with many of Washington’s most influential Arab and European allies.

Several participants argued that the talks themselves were a sign of progress. But with no end to the war in sight, there was pressure on all sides to begin chipping away at a plan that might convince Assad’s government and the vast array of armed rebel groups to stop fighting and allow world powers to focus on their shared commitment to defeat the Islamic State. Underscoring the urgency, Syrian opposition reported that a government missile barrage killed more than 40 in a Damascus suburb.

Kerry, Russian Foreign Minister Sergey Lavrov and the U.N. envoy to Syria, Staffan de Mistura, were to deliver a joint news briefing Friday.

Assad’s fate was at the center of discussions. The U.S., Saudi Arabia and others have tempered their earlier calls for Assad’s immediate ouster and now say he can remain in office for months as part of a transition if he agrees to resign at the end of the process. Russia and Iran are both providing Assad military assistance and say Syria’s leadership shouldn’t be dictated by outside forces.

Offering some hope, however, both countries have suggested greater flexibility in recent weeks. Western diplomats have spoken of various conversations with their Russian counterparts indicating that the Kremlin is not “wedded” to Assad maintaining control of the country. And senior Iranian diplomat Hossein Amir Abdollahain told The Guardian last week, “We are not working for Assad to stay in power forever as president.”

But no one has provided any clear indication of what the transition process might look like and how long it would take — or if either of the Syrian sides would be ready to support such a plan. Assad, a member of Syria’s Alawite minority, won re-election last year in a vote that Western countries called a sham and his term ends in 2021. The Sunni-led opposition wants him out immediately.

French Foreign Minister Laurent Fabius only said Assad should step aside “at one moment or another.” Saudi Foreign Minister Adel al-Jubeir said earlier this week that Assad must quit his post “within a specific timeframe.”

The comments suggested the diplomats would be happy enough to agree on a shared strategy for getting the transition started.

Russia’s deputy foreign minister, Mikhail Bogdanov, said his country and Saudi Arabia had exchanged lists of opposition groups that should be involved in future peace talks — an important question as those fighting Assad range from al-Qaida-linked militants to self-styled moderates.

There was no immediate word on any direct exchanges between Shiite-dominated Iran and Sunni-led Saudi Arabia, bitter regional rivals who have waged proxy battles for influence across the Middle East. As the full meeting of all countries began Friday, al-Jubeir was seated about as far apart from Iranian Foreign Minister Mohammad Javad Zarif as possible.

Since the start of Syria’s unrest in 2011, Assad’s future has been a stumbling block. President Barack Obama demanded that Assad leave power only months into the fighting. Russia resisted the push by blocking attempts at the United Nations to pressure the Syrian leader and insisting that any new government only be established by mutual consent of both the government and the opposition. That essentially gave Assad veto power over his would-be replacements.