Gunmen attacked a pro-government TV station Wednesday near the Syrian capital, killing seven employees in the latest barrage of violence as world powers prepared for a high-level meeting that the U.S. hopes will be a turning point in the crisis.

Invitations to Saturday's gathering in Geneva were sent by special envoy Kofi Annan to the five permanent members of the U.N. Security Council — including Syrian allies Russia and China — but not to major regional players Iran and Saudi Arabia.

The absence of those two countries, as well as the lack of any appetite for international military intervention, could make it difficult for the group to find the leverage to end the bloodshed in Syria. An effort by Annan to broker a peace plan failed earlier this year.

Diplomatic hopes have rested on Russia — Syria's most important ally and protector — agreeing on a transition plan that would end the Assad family dynasty, which has ruled Syria for more than four decades.