Iran's President Hassan Rouhani speaks to nuclear experts in Tehran, May 11, 2014. Rouhani said his country has nothing to offer except transparency in nuclear talks with world powers, rebuffing hard-liners as negotiators seek a final deal over the Islamic Republic's contested program. (Mohammad Berno/AP)

The United States is reassembling key members of the diplomatic team that held secret negotiations with Iran over its nuclear program, leading to a breakthrough agreement, and sending them to Geneva for direct talks with representatives from Tehran in hopes of making progress toward a comprehensive final deal.

The discussions involving Deputy Secretary of State William Burns, Undersecretary of State for Political Affairs Wendy Sherman and Jake Sullivan, Vice President Biden’s top foreign policy adviser, are set for Monday and Tuesday. The European Union’s political director, Helga Schmid, will sit in.

The interim deal reached in November by Iran and six world powers — the United States, Russia, China, Britain, France and Germany — limited Iran’s uranium enrichment program. In exchange, some penalties imposed against Iran were eased. But sanctions such as those targeting Iran’s oil imports have remained in place.

Those nuclear talks are scheduled to resume June 16. There is an informal deadline of July 20 for a comprehensive deal.

Iran’s official IRNA news agency said the upcoming U.S. talks would be followed by separate discussions in Rome between Iranian and Russian officials Tuesday and Wednesday. IRNA quoted Abbas Araqchi, a senior member of Iran’s nuclear negotiating team, as saying that the Islamic Republic planned to hold other bilateral talks as well with the other world powers, but those meetings had yet to be scheduled.

Iran insists that its program is for peaceful energy and medical research purposes. Much of the world fears Iran may be trying to develop nuclear weapons.

The new face-to-face talks come as the deadline approaches for world powers and Iran to translate their interim nuclear agreement into a comprehensive deal.

Talks have focused on restricting Iran’s uranium enrichment and eliminating the possibility of it producing plutonium that can be used in warheads. In exchange, the United States and others would ease penalties that have crimped Iran’s economy.

International inspectors would monitor Iran to ensure it does not ramp up activities to reach a nuclear weapons capability.

Negotiators hope to complete the agreement by July 20 but can extend the current interim arrangement for an additional six months.

That deal, reached in broad terms in November and implemented in January, provided Iran up to $7 billion in eased trading conditions for several nuclear concessions.

The Associated Press reported at the time that the compromise resulted from a series of secret meetings between U.S. and Iranian officials. The talks took place in the Middle East sultanate of Oman and elsewhere going back to 2012. They only really heated up with the election of Iran’s moderate president, Hassan Rouhani, in the summer of 2013.

Burns and Sullivan were not part of formal talks involving Iran and the world powers last year, but they participated in some secretly. They used back doors and elevators and remained hidden until journalists, including photographers, left meeting rooms.

On the idea to call them back into discussions with Iran, a senior U.S. official said the administration was engaging “in as much active diplomacy as we can to test whether we can reach a diplomatic solution with Iran on its nuclear program.”

The larger gatherings will continue. The private U.S.-Iranian sessions aim to contribute to an outcome ensuring that Iran cannot develop nuclear weapons, said the official, who spoke on the condition of anonymity to discuss the Obama administration’s thinking about the move.

— Associated Press