The latest on high-level diplomatic talks among 20 countries to reach an agreement to end Syria's civil war. All times local.

5:40 p.m.

Diplomats meeting in Vienna have agreed on a timeline for a political transition in Syria that is aimed at ending the country's civil war. However, key details remain unresolved.

At the conclusion of Saturday's talks, U.S. Secretary of State John Kerry announced agreement for talks between Syrian President Bashar Assad and the opposition to start on Jan. 1. Kerry says once an agreement on a transitional government is reached, a new constitution would be drafted within 6 months and free and fair elections would be held within 18 months.

The diplomats have agreed on a way to enforce a cease-fire but failed to agree on which groups other than the Islamic State and al-Qaida affiliates would not be eligible for the truce. They also failed to agree on Assad's role in the transition.