UN Secretary General Ban Ki-moon has called for “flexibility” at talks in Vienna between the countries backing rival sides in the Syrian civil war.
He urged the five main participants – the US, Russia, Iran, Saudi Arabia and Turkey – to abandon “national perspectives” for “global leadership”.
These are the first such talks to include Iran, which – with Russia – backs Syrian President Bashar al-Assad.
The US and its allies insist Assad cannot be part of any solution.
The four-year-old war in Syria, which began with an uprising against Assad, has left 250,000 people dead and forced half the country’s population – or 11 million people – from their homes.
Russia and Iran have recently stepped up their military involvement in the conflict, backing forces loyal to Assad.
The US, Turkey, Saudi Arabia and other Gulf Arab nations have long insisted Assad cannot play any long-term role in Syria’s future.
On the eve of the talks, Ban urged the five main participants to think beyond their immediate interests, reports the BBC.
“The longer they take their own national perspectives, the more people will suffer, and the whole world will suffer,” he said. “As I always say, there is no military solution.”
Saudi Arabia’s Foreign Minister Adel al-Jubeir earlier told the BBC that Iran must accept the removal of Assad as part of any solution to the conflict.
Jubeir told the BBC that there was “no doubt” Assad could not remain in office.
“He will go either through a political process or he will be removed by force,” he said.
Foreign ministers held informal talks in Vienna on Thursday, with the substantive discussions scheduled for Friday.
Speaking after meeting Zarif, the EU’s Foreign Policy chief Federica Mogherini said the Vienna talks would bring together “all the relevant actors playing around the same table, trying to define a common space for the beginning of a political process”.
US Secretary of State John Kerry also met Zarif on Thursday, as well as the Russian Foreign Minister, Sergei Lavrov, and the foreign ministers of Saudi Arabia and Turkey.
Foreign ministers from the UK, France, Germany, Egypt, Lebanon and the EU have also confirmed they will attend the meeting, and other Middle Eastern powers are also expected.
A Western diplomat called the Vienna talks “embryonic”, while another said that simply keeping opposing sides from walking out would count as success.
Meanwhile in Washington, White House spokesman Josh Earnest said that the US would continue supporting certain Syrian rebel groups.
He described recent US air drops of weapons and ammunition to the rebels as “a reflection of the desire… to intensify a strategy that has shown some [promise].”
Iran is believed to have spent billions of dollars over the past four years propping up Assad’s government, providing military advisers and subsidising weapons.
However, Syria’s political opposition has warned that Iran’s involvement will only complicate the meeting in Vienna.
Russia began its military intervention in Syria at the end of last month, launching air strikes in support of Assad.
Washington has accused Moscow of concentrating its air campaign in Syria on moderate opposition groups rather than on the Islamic State militant group.
