Iran talks bogged

"The talks were serious and constructive but no progress has been made," Iran's deputy foreign minister, Abbas Araqchi, told reporters after three days of talks with six major world powers in Vienna.

"We have not reached the point to start drafting the final agreement," he said, adding that differences between the sides were still too big. He gave no immediate details, but said further rounds of talks would take place in June.

A senior US official, speaking on condition of anonymity, also confirmed that the talks had been "very slow and difficult," but warned that "time is not unlimited."

He said all parties wanted to adhere to a July 20 deadline for reaching a deal to curb any Iranian nuclear work that could lead to the production of nuclear weapons, in return for the lifting of all UN and Western sanctions.

July 20 is the expiry date for the current interim agreement, concluded in November, under which Iran froze certain nuclear activities in exchange for some relief from sanctions.

Crucial issue

Diplomats say talks faltered over a dispute about Iran's capacity to enrich uranium.

The Islamic Republic says it wants to expand the number of centrifuges it has refining uranium so it can fuel a planned network of nuclear stations.

The United States and its allies, however, fear this activity could lead to the production of bombs and want Tehran to significantly reduce the number of centrifuges - roughly 10,000 - it now operates.

Further difficulties have arisen over the length of constraints on enrichment and other nuclear activities that could theoretically lead to weapons construction.

Diplomats say Iran wants all restrictions lifted after only a few years, while the West is insisting on such limits lasting for decades.

Some headway

They said, however, that some progress had been made on certain issues during the talks, with a tentative agreement in place to re-engineer a partially built reactor so that it would produce less waste plutonium. Plutonium can also be used for the core of a nuclear weapon.

In addition, they said Tehran was in principle ready to sign an agreement with the UN atomic agency that would allow the latter's inspectors to carry out fuller investigations of any atomic work.

Negotiations on the final deal began in February and involve Iran and Germany, the United States, France Britain, China and Russia.

tj/dr (Reuters, AP, AFP)