Washington and Tehran are trying to narrow their differences over Iran's nuclear program in talks set to begin Friday in Geneva, Reuters reported based on reports by the Islamic Republic's state news agency, IRNA.

Negotiators from Iran, the five permanent members of the U.N. Security Council and Germany failed to meet a self-imposed deadline in November to end the 12-year standoff over Tehran's nuclear capabilities. Top U.S. and Iranian diplomats will now again try to strike a deal.

"The talks between Iran and U.S. deputy foreign ministers will be on Friday and Saturday," said Abbas Araqchi, Iran's senior nuclear negotiator. "Iran's Foreign Minister (Mohammad Javad Zarif) and (U.S. Secretary of State) John Kerry will join the negotiators on Sunday and Monday."

At the initial stage of the process, the American delegation will be led by Wendy Sherman, the top U.S. negotiator. The State Department insisted the bilateral talks were taking place in the context of broader negotiations with Iran.

Araqchi hinted that if Washington and Tehran reached agreement, negotiators from China, France, Germany, Russia and the United Kingdom might join the consultations, Agence France-Presse noted.

"After four days of bilateral discussions between the Iranian and U.S. nuclear delegations, they could continue with the participation of all members of the (U.N. Security Council, plus Germany)," the nuclear negotiator was quoted as saying by the IRNA.

The State Department, meanwhile, announced the European Union's deputy foreign policy chief, German diplomat Helga Schmid, would participate in the negotiations.

If the stalemate over Iran's nuclear program could be resolved, Tehran might benefit from an end to crippling sanctions and warmer relations with the West, CNN reported; a lack of an agreement, however, would most likely increase tensions and could lead to more punitive measures/.

Tehran insists all sovereign nations are entitled to develop nuclear power for peaceful purposes. But Western powers have accused Iran of trying to shield a weapons program behind the purportedly benign energy project.