The US, Russia, Saudi Arabia, Turkey, Iran, Egypt, European Union and France will meet in Vienna today, Friday 31 October with the aim of achieving a political settlement to help end the Syrian war. Russia and Iran both support the Syrian President Bashar al-Assad. The US and Saudi Arabia would like a new leader instead of Bashar al-Assad.
The four-year-old war in Syria, which began with an uprising against Mr 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 Mr Assad. Iran is believed to have spent billions of dollars over the past four years propping up Mr Assad's government, providing military advisers and subsidising weapons.
Why is there a war in Syria?
Anti-government protests developed into a civil war that, four years on, has ground to a stalemate, with the Assad government, Islamic State, an array of Syrian rebels and Kurdish fighters all holding territory.