Diplomats were cautious about any immediate progress in talks as they met Friday, though U.S. Secretary of State John Kerry, who has described the meetings as the best chance to "chart a course out of hell," said he was "hopeful" going in.
"Optimistic? I'm hopeful," Kerry told reporters in Vienna before starting the meeting, which featured representatives from at least 18 interested parties. "There's a lot of work to do but I am hopeful."
Senior American and Arab diplomats said the U.S. is seeking agreement on a roadmap for President Bashar al-Assad's transition from office, telling CNN the plan being discussed would lead to a transitional government or council. Under the plan, Assad would hand over powers to the transitional body before elections were held.
However, the parties at the talks have different ideas about how rapidly -- and even whether -- they would like to see Assad leave power, challenging efforts to reach an understanding.
After talks wrapped Friday, High Representative of the EU for Foreign Affairs and Security Policy Federica Mogherini tweeted that talks were "difficult but constructive."
"8 hours of substantial #SyriaTalks in Vienna. Difficult but constructive: we have enough common ground to start UN led political process," she tweeted
Kerry outlined six of the major points of agreement in a press conference following the talks: that Syria's state institutions will remain intact; that the rights of all Syrians, regardless of ethnicity or religious denomination, must be protected; that it is imperative to accelerate all diplomatic efforts to end the war; that humanitarian access must be assured throughout the territory of Syria, and the participants will increase support for internally displaced persons, refugees and their host countries; and that ISIS and other terror groups be designated by the UN Security Council, and agreed by the participants must be defeated.
Friday's talks come as news broke that the U.S. is set to deploy U.S. troops on the ground in Syria for the first time to advise and assist rebel forces combating ISIS, multiple officials said.
They also come after news that at least 40 people were killed and 100 were wounded in rockets attack near Damascus earlier in the day, the Syrian Observatory for human Rights said in statement.
The group said the Syrian government forces have launched rockets attack targeting a marketplace in town of Duma in Damascus suburbs. The group also said that the number of casualties is likely to increase as some of the wounded are in critical condition.
Still, Kerry said Thursday that even if the talks on Syria's future didn't reach an immediate political solution, they represented the best hope forward after the bloody civil war that has killed more than 250,000.
"What that transitional government could look like, who would be part of it, how they would meet and at what frequency -- all of this is up in the air," one senior State Department official said, noting that Kerry is just seeking agreement on the framework.
Some 18 nations, plus the European Union, were invited to the meeting. They include Russia and, for the first time, Iran.
With so many competing agendas at the table, one diplomat described Kerry's role as a "maestro" trying to bring the dueling positions closer to the middle.
But with everyone singing from different sheet of music, U.S. officials and diplomats signaled even firm agreement Friday on the broad strokes appeared slim.
"The Saudis, Turks and Qataris are pushing hard in one direction, the Russians and Iranians are pushing in another. Some are in the middle," one Arab diplomat said.
"How do you balance those set of demands?" he asked. "Everyone is agreed we need a way out though a negotiated settlement. But once you get into the nitty-gritty, the time frames and the specifics, it all falls apart."
The main sticking point among the major powers remains the future of Assad. The U.S. and its European and Arab allies want to see Assad hand over power fairly quickly, while Russia wants to organize a political process by which the transitional government can then decide on Assad's future first, after which Syrians can decide his future.
Friday's talks come weeks after Russia began a bombing campaign to put pressure on opponents of Assad. While the U.S. and Arab countries had once called on Assad to leave power as the first step to a transition, they have tempered that call as the war has dragged on and as Russia comes to Assad's assistance.
Meanwhile Iran, which agreed to join the talks for the first time, is the one country at the table that still has not signed onto the idea of a transition from Assad.
"The Saudis won't sign on unless there is a guarantee that at end the end of this period, say it's 12 months, that Assad is gone," one Arab diplomat said. "So far the Russians have not said they are willing to commit to that, and the Iranians haven't agreed to him going at all."
Administration officials have expressed cautious optimism that Russia will support Assad's eventual transition from power, even if he is allowed to remain for a period of time. The time frame for his departure has ranged from six to 18 months.
The last major peace talks, held in February in Geneva, failed to produce an agreement. But it marked the first time the Syrian government and representatives of the armed opposition sat at the negotiating table.
This time, the plan being discussed appears to have little role for the Syrians themselves. There seems to be a disconnect between the major power brokers meeting in Vienna and the demands of the Syrians, who were not invited to the meeting.
But U.S. officials said a key aspect of the conversation will be a renewed effort to better organize Syria's fragmented opposition.
Michael Ratney, the U.S. coordinator for Syria, flew this past weekend to Turkey to meet with both the political opposition and rebel leaders to fill them in on the ongoing diplomacy.
"They are not ready," one senior U.S. official said. "They are not capable of sitting down at this table because they do not even agree with themselves."
After five years of the U.S. failing to organize the political opposition, Joshua Landis of the University of Oklahoma said Kerry is in the unenviable position of letting Russia run a political process that won't ultimately get rid of Assad.
"Americans keep clinging the notion of regime change on the cheap and Russia keeps clinging to the notion they can retake the country," Landis said.
Landis said that Russia has an incentive to continue the talks so Saudi Arabia does not make good on threats to increase its support for jihadis in Syria to fight against Russian forces.
"When the (Syrian) regime and Russia talk about a political solution, they are talking about using their military force in order to kill or force the jihadists out and create an environment where the more moderate militias have to come in from the cold and make a deal with the regime," according to Landis. "You can sugarcoat it by saying there will be elections, but elections over the past 50 years have all turned out the same way. Assad isn't going anywhere. "
But U.S. officials and European diplomats stress that both Russia and Iran have an incentive to de-escalate the conflict.
"Iran has put billions of dollars into this conflict that isn't going anywhere and Russian intervention came in an effort to stop the regime from falling," one European diplomat.
"Clearly the Assad question is the big issue," the diplomat continued. "But the fact everyone is able to sit at the same table is significant, and we need to test if we can find any common ground. If we start from the fact that we can't, we have to just admit defeat."