Hasan Rowhani, Iran's top nuclear negotiator, said on Thursday that Tehran would resume some nuclear activities because it could not continue nuclear negotiations with Europeans.
"Continuation of negotiations in their present format is not possible for us," Rowhani told Ian state-run television.
"The basic point that the Islamic Republic of Iran will resume part of its nuclear activities in the near future is definite," Rowhani said.
Earlier, diplomats in Vienna had said Iran was considering backing away from its threat to immediately resume activities that can be part of the process of making nuclear weapons, in an apparent attempt to defuse a showdown with key European nations.
One of the diplomats said that Iranian government officials in Tehran were discussing maintaining their freeze on uranium conversion because of a warning from key European countries that such a move would result in "consequences ... that would only be negative for Iran", diplomatic code for likely action by the UN Security Council.
Iranian journalist Muhammad Sadiq al-Hussaini told Aljazeera that Iran's resumption of its nuclear programme would serve as a warning to the European tripartite negotiating delegation to not give in to US pressure to abandon talks.
Another Iranian senior official affirmed on Thursday that Tehran would resume a "noticeable part" of uranium conversion activities.
"Based on the reviews and decisions which were made, we are going to restart a small part of the suspended activities," Gholam Reza Aghazadeh, a vice-president and head of Iran's Atomic Energy Organisation, told state television.
"Continuation of negotiations in their present format is not possible for us. The basic point that the Islamic Republic of Iran will resume part of its nuclear activities in the near future is definite"
Hasan Rowhani, Iran's top nuclear negotiator
He said "probably a noticeable part of UCF", or work at a uranium conversion facility near the central city of Isfahan, would be resumed.
Aghazadeh added that the "exact date of the restart will be given to me momentarily".
Russia plans to make its first delivery of nuclear fuel to Iran at the end of this year or early next year, a senior Russian nuclear official said on Thursday.
The delivery comes under a landmark agreement to fire up the country's first atomic power station.
"They have to start to fire it up mid-2006. The fuel has to be at the plant six months before that," Alexander Rumyantsev, the head of the Russian atomic agency, said in an interview to be published on Thursday.
Iran is to resume work on its
uranium conversion activities
Under the accord between Russia and Iran, signed in February, Russia is to send nearly 100 tonnes of fuel in several consignments under the supervision of the International Atomic Energy Agency (IAEA).
"All the necessary precautions have been made in line with international standards," Rumyantsev said.
The United States alleges that the Bushehr nuclear power plant in southern Iran is part of a cover for weapons development.
Washington is convinced that Iran is seeking to build atomic weapons - charges that Tehran denies - and has been trying to convince Moscow to halt its nuclear cooperation.
As a concession to Western concerns, Russia will fuel the reactor on the condition that Iran sends back spent fuel, which could potentially be upgraded for weapons use.
Tehran initially rejected the condition, but eventually relented after two years of negotiations.