Iran is considering joining the international talks on Syria's future, expected later this week in Vienna, after receiving an official invitation for the gathering through Russia's envoy.

Foreign ministry's spokeswoman, Marzieh Afkham, confirmed the invitation and said Wednesday that "Iran is thinking about attending this meeting." Her quotes were carried by the official IRNA news agency.

She says Foreign Minister Mohammad Javad Zarif and his Russian counterpart, Sergey Lavrov, discussed ways to resolve the Syrian crisis both late Tuesday and on Wednesday.

The invitation came after the United States declared itself ready to engage long-time foe Iran if it might help halt Syria's four-year civil war.

Iran is a key ally of Syrian President Bashar Assad and has provided his government with military and political backing for years.