"There is a belief among the European negotiators that if they give Iran political, security and economic incentives, Iran will give up enrichment," nuclear negotiator and top cleric Hassan Rowhani told state media.

"So during this trip we made it quite clear that enrichment is not negotiable," added Rowhani, who was speaking upon his return to Tehran from a visit to Paris and Berlin.

Britain, France and Germany have been trying to persuade Tehran to permanently abandon its capacity to produce enriched uranium -- which can be directed to both civil and military uses -- in return for a package of incentives.

The diplomatic effort is aimed at securing "objective guarantees" that Iran will not produce nuclear weapons.

Following talks in Paris last year, Iran pledged to suspend its fuel cycle work while the negotiations are in progress, but has also consistently warned that the freeze on enrichment is only temporary.

"Based on the Paris agreement, we are trying to give objective guarantees so that we could resume enrichment and keep up trust building," said Rowhani, still at odds with the European position.

He added that the end of the current Iranian year on March 20 "is the end of three months of negotiations, and will be good time to evaluate if we should continue the negotiations or not."

Iran maintains that enrichment for peaceful purposes is permitted under the nuclear Non-Proliferation Treaty (NPT), and insists it only wants to enrich uranium to levels required to fuel a nuclear power station.

The United States in particular accuses Iran of using the atomic energy drive as a cover for weapons development, while many European diplomats see the fuel cycle drive as Iran seeking a "strategic option" to build an atomic bomb.

A two-year probe by the International Atomic Energy Agency (IAEA), the UN body that monitors the NPT, has uncovered plenty of suspect activity by Iran but no conclusive "smoking gun" to prove that the country has military plans for its programme.

Iran's foreign ministry spokesman Hamid Reza Asefi also moved to clear up an apparently contradictory positions over the possible presence of the United States in the negotiations, after Rowhani said he would welcome US "help".

"We welcome US help, but that does not mean a US presence. One way they can help is by not entering the negotiations. There is no need for a US presence in the negotiations," Asefi told reporters. "There is no contradiction."

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