FRANKFURT, April 5: The United Nations nuclear chief Mohamed ElBaradei said on Monday he was running out of patience with Iran over its failure to fully assure the international community that it does not have a secret nuclear weapons programme.

Mr ElBaradei, on his way to Tehran, said the 35-member board of governors of the International Atomic Energy Agency (IAEA) was "impatient with Iran's cooperation".

The international probe into Iran's programme "cannot go on forever. We have to discuss how to accelerate cooperation," he said. "We need to satisfy ourselves there are no undeclared nuclear activities in Iran."

The IAEA director general is due in Iran on Tuesday for talks on the nuclear issue, although Tehran insists it is not hiding any of its facilities from UN inspectors.

"We have a transparent and constructive cooperation with the agency, and this will continue," Iranian foreign ministry spokesman Hamid Reza Asefi told reporters on Sunday.

Iran also declared that its resumption of work on a key part of the nuclear fuel cycle was not a violation of its commitment to suspend uranium enrichment activities.

In a deal with the IAEA brokered last year by the European Union's big three - Britain, France and Germany - Tehran agreed to suspend uranium enrichment and related activities while UN inspectors delved into its programme.

However, an IAEA board resolution on March 13 condemned Iran for failing to report sensitive nuclear activities, such as the possession of designs for sophisticated P-2 centrifuges that can make bomb-grade uranium.

Since then, Mr ElBaradei said, Iran has delayed a crucial IAEA inspection mission to research the P-2 question. "We were supposed to do the P-2 (investigation) last month and now we are going in on April 10," Mr ElBaradei, making his third trip to Iran since February last year, told reporters on a stopover in Frankfurt.

He said a date had yet to be set for Pakistan to allow IAEA inspectors in to the country to carry out so-called "environmental sampling" to compare certain key components with those allegedly sold on the international black market to Iran.

Iran has always claimed that the presence of highly enriched uranium (HEU) discovered by the IAEA was due to contamination from particles on the imported components. The HEU can be used both as nuclear fuel in civilian reactors or as the raw material for an atomic bomb. -AFP