Further talks on ending the Syrian conflict could occur as soon as October 30, and the talks eventually must involve Iran, a U.S. State Department spokesman has said.
"At some point...we know there's going to need to be a conversation with Iran towards the end of a political transition there," spokesman John Kirby said as the United States sought to organize the next round of talks.
U.S. Secretary of State John Kerry and counterparts from Russia, Saudi Arabia, and Turkey met in Vienna on October 23 to discuss a political settlement in Syria.
The talks produced little progress amid long-standing disagreements over the future of Syrian President Bashar al-Assad.
Kirby said Iran's role in the Syrian conflict, including its support for Assad and Lebanon's Hizballah, has been unhelpful, but eventually it should join the talks.
"They are a stakeholder in this process. They do have a relationship with the Assad regime," Kirby said.
Thus far, Iran has mostly sent military advisers to Syria. Recently, it has mobilized Shi'ite militia fighters, including Iraqis and some Afghans, to fight alongside Syrian government forces.