Syria talks to test if Iran, Russia 'serious' on peace: Saudi

International talks in Vienna this week will test whether Russia and Iran are "serious" about a political solution to the war in Syria, the Saudi foreign minister said on Wednesday.

"If they're serious we will know, and if they're not serious we will also know and stop wasting time with them," Adel al-Jubeir said at a press conference with visiting British Foreign Secretary Philip Hammond.

The two-day talks beginning Thursday will "test the intentions of the Syrians and the Russians," Jubeir said.

He said the meetings will be a chance to "bridge the gap" between Iran and Russia on the one hand, and other countries on the role of President Bashar al-Assad.

"There has to be certainty that Bashar al-Assad will leave," Jubeir said.

For his part, Hammond said that while Russia and Iran think Assad should be able to stand for re-election, so that the Syrian people can decide on his future, Assad has "too much blood on his hands." 

Iran earlier confirmed that Foreign Minister Javad Zarif will join his counterparts from Russia, the United States, Turkey and Saudi Arabia at the talks.

The inclusion of Iran -- a key backer of President Bashar al-Assad -- marks a crucial shift after Tehran was excluded from earlier talks, mainly because of opposition from Riyadh.   

The Vienna discussions are expected to be the first time all major international players in the conflict, linked to the nearly five-year war, will participate.

Iraq and Egypt will also be joining the talks in Vienna but on Friday.