The head of the International Atomic Energy Agency has appealed to Iran to suspend the enrichment of nuclear material, at least for the time being. But an Iranian envoy told reporters in Vienna that his country has a legal right to enrich uranium.

The head of the IAEA, Mohamed ElBaradei, says the agency still needs more information from Iran on advanced centrifuges and potentially arms-related research. Iran failed to mention the advanced centrifuges in a report given to the IAEA at the end of last year.

The report was supposed to be full and comprehensive, but Iran said the omission happened because of time pressures.

Iran claims it did no work on the centrifuges between 1995 and 2002 but the IAEA says it lacks sufficient assurances. Mr. ElBaradei says Tehran should suspend enrichment-related activities until such questions surrounding the nature of Iran's nuclear program can be cleared up.

"Iran has reversed some of its earlier decision with regard to testing or producing some enrichment components," he said. "I am clearly calling on Iran as well as many board members that at this delicate phase while we still verify Iran's past program that it is in the interest of Iran to do its utmost to continue to pursue, fulfill, a policy of full transparency and to show full and active cooperation."

Mr. ElBaradei said the suspension of uranium enrichment would be a key confidence-building step by Iran.

But Seyed Hossein Mousavian, of the Supreme National Security Council in Tehran, told reporters outside the IAEA board meeting Iran had already done enough.

"Enrichment from the beginning has been a voluntary decision from Iran to create confidence," he said. "This was decided in October 2003. From October 2003 we believe we have taken maximum steps of confidence building. First we have given a full report about past and present nuclear activities of Iran. We have given full access to the IAEA for all inspections they need."

The envoy said Iran has a legitimate right to enrich uranium, and added there are sensitive discussions currently going on with major European countries on the subject.

France, Germany, and Britain have called for Iran to halt enrichment. The three countries are expected to put forward a resolution to the IAEA Board later this week calling for the agency to give Iran until November to prove its nuclear program is peaceful, and not military, as the United States believes.

The Board has been threatening for months to refer the issue to the U.N. Security Council, if it is not satisfied with Iran's cooperation on nuclear issues.