VIENNA - Iran will convert more of its higher-grade enriched uranium into reactor fuel under an interim nuclear deal with six world powers, making the material less suitable for building atomic bombs, a diplomatic source said on Monday.

Iran and the United States, France, Germany, Britain, China, and Russia failed to meet a Nov. 24 deadline for resolving their dispute over Tehran's nuclear program. They gave themselves until the end of June for further negotiations.

Source: Iran to Turn Uranium Into Reactor Fuel

It was the second time this year they had missed a self-imposed target for a comprehensive agreement to scale back Iran's nuclear program, in exchange for phasing out sanctions that are hurting its oil-dependent economy.

Source: Iran to Turn Uranium Into Reactor Fuel

As a result, a preliminary agreement reached late last year, designed to buy time for the talks on a final settlement, will remain in force. Under its terms, Iran halted its most sensitive nuclear activity in return for limited sanctions easing.

Source: Iran to Turn Uranium Into Reactor Fuel

Accordingly, Iran earlier this year eliminated its stockpile of uranium gas enriched to a fissile concentration of 20 percent, a relatively short technical step from weapons-grade material. A large part of it was processed into oxide.

When the deal was first extended in July, Iran undertook to move further away from weapons-usable material by converting 25 kg of the higher-grade uranium oxide - a quarter of the total - into nuclear fuel during the initial four-month extension.

The source, who declined to be named, said under the new extension Iran would continue this work and suggested about 5 kg would be converted per month. The details of the extended agreement have yet to be made public.

In July, a senior U.S. official said that once the oxide had become fuel plates for a Tehran research reactor, Iran would “find it quite difficult and time-consuming” to use it in any nuclear bomb “breakout scenario.”

Iran denies Western allegations that it has been seeking to develop the capability to build atomic arms, saying its nuclear program is a peaceful project to generate electricity.

Under the seven-month extension of the negotiations, Iran will receive about $700 million per month of its oil revenue frozen in banks abroad.