Germany, which has led talks for the EU with Iran over its nuclear program along with its partners Britain and France, warned against any false moves that could jeopardize the long-running negotiations aimed at keeping Tehran from developing a nuclear bomb.

"The German government calls on Tehran not to undertake any unilateral steps that would violate the agreement from Paris," a foreign ministry spokesman told reporters, referring to a pledge Iran made in November to suspend uranium ore enrichment.

Troubling news

The spokesman, Jens Plötner, said Germany was "troubled" by Iran's aim to begin limited work on its nuclear program again Monday by resuming activities at its Isfahan plant, a facility used for uranium conversion.

The statement followed an ultimatum Sunday that Tehran would resume uranium conversion if the so-called EU-3 countries failed by Monday to come up with a package of trade and security incentives.

However, the Europeans told Tehran they would make the offer by August 7, after the ultra-conservative Mahmood Ahmadinejad takes office Thursday as Iran's new president.

Plötner said that Britain, France and Germany intended to stick with a timetable agreed in May in Geneva in which the three countries would put forward a new "comprehensive" proposal by early August.

He added the offer would be presented to Tehran "in a few days."

"In this context, a resumption of uranium conversion would be a completely unnecessary step," he said.

"We are still ready to negotiate with Iran on the basis of our previous agreements. But now it is up to Iran not to miscalculate."

Iran to face UN sanctions?

Plötner declined to "speculate" about potential consequences if Iran re-launched its nuclear conversion program, as Paris and London echoed the concerns.

Previously the EU-3 have warned that if Tehran re-launches nuclear conversion they would support the call by the United States for Iran to be brought before the UN Security Council to face possible sanctions.

The United States has accused Iran of seeking to develop nuclear weapons -- a charge Tehran denies -- and has backed the EU diplomatic effort to resolve the crisis.

"There is no economic nor technical justification" for Tehran resuming nuclear activities, a move that "surprised" Paris, French foreign ministry spokeswoman Cecile Pozzo di Borgo told reporters.

Paris described the Europeans' propositions to Iran as "generous".

"In particular, they recognize Iran's rights within the NPT (nuclear non-proliferation treaty) and the option to develop a safe, economically viable and non-proliferating nuclear program," said Pozzo di Borgo.

Clarification needed

Britain said it was "seeking clarification" of Iran's intentions and reviewing a letter sent by Tehran to the International Atomic Energy Agency (IAEA), the United Nations nuclear watchdog.

"We are seeking clarifications on their intentions," a ministry spokesman said. "We are studying the letter sent by the Iranians."

Meanwhile the European Commission -- the EU's executive arm -- voiced support for negotiating with Tehran and said it hopes "no steps will be taken in coming days that would endanger such a negotiated solution," a commission spokesman said.

Uranium enrichment is a process that makes fuel for civilian nuclear power plants but can also be the explosive core of atom bombs. The conversion process changes uranium ore into the uranium gas that is the feedstock for enrichment.

The IAEA has been investigating Iran's nuclear program since February 2003 following US charges that the Islamic republic is secretly developing nuclear weapons.