MOSCOW ¨C Russia signed a deal Tuesday to build new nuclear reactors in Iran as another round of talks that aim to prevent the Islamic Republic from obtaining atomic weapons ended without a breakthrough.

The deal foresees the expansion of the existing Bushehr plant with two reactors and an option for two more, as well as four units elsewhere, according to an emailed statement by Moscow-based Rosatom Corp. U.S. Secretary of State John Kerry, former European Union foreign policy chief Catherine Ashton and Iranian Foreign Minister Mohammad Javad Zarif ended two days of talks in Oman Monday without reporting progress.

¡°There wasn¡¯t any discussion on uranium enrichment in Iran, either in the negotiations or the documents¡± signed, Sergei Novikov, a spokesman for state-owned Rosatom, said by phone. ¡°All we are offering is the localization of some equipment needed for construction.¡±

The diplomats are seeking an accord that would ease concerns that Iran may develop nuclear weapons, and lift sanctions that have devastated the country¡¯s economy and curbed oil output. Russia built Iran¡¯s only functioning nuclear power plant, in Bushehr province, as Iranian officials say they want to boost atomic power generation to feed growing demand.

Ali Akbar Salehi, head of Iran¡¯s Atomic Energy Organization, and Sergei Kiriyenko, the chief executive of Rosatom, signed the accord in Moscow.

Separately, another round of talks started Tuesday between officials from Iran and Germany, France, the U.K., the U.S., Russia and China. Unresolved issues include the scope of Iran¡¯s uranium-enrichment program, how and when to lift sanctions, and how long Iran¡¯s nuclear program must remain under international inspections and safeguards.

A concluding round of talks at the foreign-minister level is scheduled for Nov. 18 in Vienna, less than a week before an interim accord that offered limited sanctions relief in exchange for concessions from Iran expires.

The process ¡°will be set back another two years¡± if a final deal isn¡¯t reached by the Nov. 24 deadline, German Foreign Minister Frank-Walter Steinmeier said Tuesday.