The world powers working to promote a resolution to Syria's civil war plan to resume talks on Tuesday in Vienna. 

The 17-member international Syria support group will participate. The group is co-led by the US and Russia, and includes Turkey, Iran, and Saudi Arabia. 

US Secretary John Kerry said the Vienna talks aim to build on a US-Russia agreement announced to try to restore a nationwide cease-fire. He said negotiators will discuss the truce's duration and enforcement, plus the political process.