"I keep calling on Iran to be as pro-active (as possible) and to go out of its way to help us bring some of these issues to a closure," ElBaradei told reporters as he went into a meeting of the IAEA's 35-nation board of governors.

"In view of the past undeclared nature of significant aspects of Iran's nuclear program, a confidence deficit has been created," ElBaradei said in his speech to the board, a copy of which was obtained by AFP.

The United States charges that Iran has a clandestine nuclear weapons program and wants the IAEA to bring Tehran before the UN Security Council for possible sanctions.

But ElBaradei says that while Iran hid sensitive nuclear activity for almost two decades, "the jury is still out" on whether Tehran is trying to develop atomic weapons.

ElBaradei said Iran has told the IAEA about a letter offering weapons technology it received in 1987 from a black market ring run by Abdul Qadeer Khan, the father of Pakistan's nuclear bomb.

ElBaradei said "the offer was extensive" but Iran said "they did not obviously take these people up on the entirety of this offer but that is the kind of information we need."

A diplomat close to the IAEA told AFP the agency has only seen part of the letter and needs more information.

ElBaradei said the IAEA was also continuing to verify "Iran's voluntary suspension" of nuclear fuel cycle activities as Tehran attempts to trade this in for economic and security benefits in negotiations with the European Union.

The European Union backed Russia Monday after Moscow struck a landmark deal to help Iran power up the Islamic state's first nuclear reactor, despite US protests that this is part of the cover for weapons development.

Moscow's IAEA ambassador Grigory Berdennikov told AFP in Vienna that the deal was in fact a "positive" step for non-proliferation since spent fuel will be returned.

Uranium that has been used in a reactor can be used to separate out plutonium, which can make atomic bombs, but the Iran-Russian deal stipulates that the spent fuel will be returned to Russia.

Meanwhile, White House spokesman Scott McClellan said the United States is studying ways to support Iran's talks with the EU.

McClellan did not however confirm a Washington Post report Monday that Washington was considering offering incentives to Iran in exchange for giving up nuclear plans.

The new willingness comes after President George W. Bush's talks with German and French leaders in Europe last week, the Post said.

Incentives under consideration by the United States include eventual membership of the World Trade Organization and facilitation of Iran's efforts to obtain spare parts for its ageing passenger airplane fleet, the Post said.

Iran, which seeks to legitimize its nuclear program, would like to see the IAEA drop its two-year-old inquest into this program and certify that Tehran's atomic intentions are peaceful.

But ElBaradei said: "We still have work to do. I cannot put any time frame on that dossier ... particularly in light of the clandestine nature of the (Iranian) program for almost two decades."

IAEA deputy director for verification Pierre Goldschmidt is to report to the board this week to say that Iran has not yet allowed IAEA experts to follow up on inspections of Iran's Parchin military facility, where Washington charges Tehran is simulating testing of atomic weapons, diplomats said.

The IAEA is also looking into other new matters, such as tunnels being built that could hide nuclear material or equipment, and has still not resolved two lingering major questions -- that of Iran's research into sophisticated centrifuges that enrich uranium, which can be weapons-grade, and highly enriched uranium contamination found in Iran.

But ElBaradei said progress was being made in these two areas.

Meanwhile, ElBaradei said North Korea's recent declaration "that it possesses nuclear weapons is a matter of utmost concern and has serious security implications and highlights yet again the importance and the urgency of finding a diplomatic solution through dialogue."

North Korea kicked IAEA inspectors out in December 2002 and withdrew from the nuclear Non-Proliferation Treaty (NPT).

It now says it has atomic weapons and has withdrawn from six-party talks on its nuclear program.

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