VIENNA -- Talks among international foreign ministers on ending the Syrian conflict are under way in Vienna.
Syrian President Bashar al-Assad's main regional backer, Iran, is taking part for the first time in such a meeting on the 4 1/2-year war, along with Damascus's other key ally, Russia.
Diplomats have played down expectations of any breakthrough.
Both Moscow and Tehran insists that Assad must be part of any transitional government, while the United States and its Western and Gulf allies want the Syrian leader to step aside.
On October 29, Iranian Foreign Minister Mohammad Javad Zarif held separates meetings with U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov, whose country launched a campaign of air strikes against foes of the Syrian government a month ago.
Kerry later met with Lavrov and the foreign ministers of Turkey and Saudi Arabia in a nearly hourlong meeting ahead of multilateral talks on October 30.
U.S. State Department Counselor Tom Shannon said Kerry aims to test the extent to which Russia and Iran are “prepared to work broadly with the international community” and convince Syrian President Bashar al-Assad “that during a political transition process he will have to go.”
Shannon said Kerry also wants to “determine whether or not...their public commitment to fighting [Islamic State militants] and terrorism is a meaningful one.”
The talks will expand on October 30 and will include high-level representatives from the United States, Russia, Germany, France, Great Britain, Italy, Iran, Iraq, Egypt, Lebanon, Qatar, the United Arab Emirates, and Jordan.
European Union foreign policy chief Federica Mogherini and the United Nations special envoy for Syria, Staffan de Mistura, also are attending.
But neither Syria's main political opposition body nor representatives of Syria's armed opposition have been invited.
The Syrian opposition has objected to Iran's participation, saying it will only complicate efforts to map out a political transition that guarantees the departure of Assad.
Bashar al-Zoubi, a commander of the Yarmouk Army within the opposition Free Syrian Army, says Iranian support for Syrian President Bashar al-Assad's regime makes Tehran "part of the problem and not the solution."
George Sabra, a member of the opposition Syrian National Coalition, says the failure to invite Syrians to the Vienna meeting reveals a "lack of seriousness."
A statement from Bassam Abdullah, a member of the opposition Syrian National Coalition, warned on October 29 that rebels would reject any role for Assad in the transition "even for one day."
Abdullah dismissed the Vienna initiative as an attempt to allow Assad's military to regain territory it had lost to opposition fighters.
U.S. officials have said that progress in Vienna is likely to be elusive.
Washington, Saudi Arabia, Turkey, and Qatar want Assad to leave power as part of a transition plan.
In an interview with the BBC, Saudi Foreign Minister Adel al-Jubeir warned on October 29 that Assad “will go either through a political process or he will be removed by force."
France, which also wants Assad to step down from power, said it had worked with its Western allies on the details of a proposal that would guarantee Assad's departure "within a precise timetable."
But Russia and Iran say his exit from power cannot be a precondition for a political settlement.
Kerry on October 28 said the Vienna talks were not likely to find an immediate political solution, but represented "the most promising opportunity for a political opening we have seen."
Kerry said the challenge faced in Syria today "is nothing less than to chart of course out of hell."
Kremlin spokesman Dmitry Peskov said Russia wanted a "widening of the dialogue" on Syria.