Negotiators kicked off a fresh round of talks over Iran's nuclear program in Vienna on Thursday, seeking to revive the 2015 nuclear deal.

Iran's top nuclear negotiator Ali Bagheri Kani on Thursday met with the European Union's Iran nuclear talks coordinator Enrique Mora in Vienna, Fars News Agency reported.

In late June, Qatar hosted indirect talks between Tehran and Washington in the hope of getting the process back on track, which failed to make a breakthrough.  

In a last-ditch effort, EU foreign policy chief Josep Borrell submitted a compromise proposal last month and called on the parties to accept it to avoid a "dangerous nuclear crisis".   

Borrell said the draft text includes "hard-won compromises by all sides" and "addresses, in precise detail, the sanctions lifting as well as the nuclear steps needed to restore" the 2015 pact. 

(With input from AFP)