ElBaradei will leave Vienna on Wednesday to arrive in Tehran on Thursday, IAEA spokesman Mark Gwozdecky told AFP.

The visit comes 15 days before a deadline expires for Iran to dispel suspicions it is pursuing a nuclear weapons programme.

"As agreed with Iranian officials, the purpose of Dr ElBaradei's visit would be for Iran to provide the IAEA during that visit with all the remaining information required to clarify important questions that are still outstanding about Iran's nuclear programmes," IAEA spokeswoman Melissa Fleming said.

The IAEA last month threatened to refer Iran to the UN Security Council for breach of the nuclear Non-Proliferation Treaty (NPT) if it failed.

Inspectors' concerns focus in particular on traces of highly enriched uranium found on two samples they took from suspect nuclear sites.

Iranian state-run media said Monday that the government was due to start talks with the IAEA next week on calls for it to sign an additional protocol of the NPT allowing for snap inspections of nuclear sites.

Iran has come under intense pressure from the United States, which accuses it of trying to develop nuclear arms, and Europe to sign the protocol, but has dithered and demanded guarantees that its military secrets would not be compromised.

On Monday Ali Rabii, an advisor to President Mohammad Khatami, told the state IRNA news agency Iran would next week set out its "positions and concerns" regarding the signing of the protocol, "the technical and economic considerations involved, and its interests and national security needs."

Iran's representative to the Vienna-based IAEA, Ali Akbaar Salehi, insisted in the daily Iran that the country has stepped up cooperation with the watchdog since an IAEA team visited Tehran early this month.

"The pace of cooperation has quickened since the recent Tehran talks and we are counting on it accelerating still further in the coming weeks now that we have drawn up a work plan," he said.

ElBaradei last week told the Financial Times newspaper: "They have promised information will be forthcoming but it has not yet been provided.

"The central question is whether Iran has any enrichment activities that we have not been informed about. On that question I have not got satisfactory information."

A five-member team of IAEA inspectors were due to leave Iran on Monday and and was scheduled to be replaced by a new one in about a week.

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