The US wants Iran to participate in Syria peace talks, sharply moving away from its traditional stand. Washington has said representatives from Tehran, a staunch ally of the Assad regime in Syria, were likely to be invited for the upcoming discussions in Vienna.
Global leaders including US Secretary of State John Kerry and Russia's Foreign Minister Sergei Lavrov will take part in the multi-pronged diplomatic initiative in the Austrian capital. The talks begin on 29 October.
White House officials have not said which nations would extend the invitation to Iran, a key player in the Syrian crisis. However, Russia, a close ally of Syrian President Bashar al-Assad, has said it has already formally invited Tehran.
The Obama administration has long been averse to Iran's presence in the talks because Tehran, along with Russia, insists on Assad's role in any planned transition. A previous invitation to Iran by UN Secretary General Ban Ki-moon had to be withdrawn upon objections by the US and other opponents of Assad.
"Whether they come or not is up to Iranian leaders. It's important for us that key partners are in these discussions... They [Iran] could be a key partner, but they are not now," State Department spokesperson John Kirby told reporters.
"So I can't tell you exactly what the outcome of the meetings on Friday is going to be or if it's the last chapter - I rather doubt that."
US officials say their bid to engage Iran is sincere and has come after efforts by American diplomats to overcome Saudi Arabia's opposition to Iran's presence.
When asked about Iran's role in the upcoming talks, Kirby said: "It's important for us to make sure that key partners are in these discussions. The secretary [of state] wants to encourage these kind of discussions and conversations as we continue to look for solutions to what is a difficult political situation in Syria."
Iran has invested heavily in the bloody Syrian conflict, which has claimed more than 220,000 lives. It has deployed hundreds of troops in Syria in support of Damascus, spending billions of dollars in the past four years.