The International Atomic Energy Agency says it is trying to find out if Iran accepted in its entirety, what is termed, an "extensive offer" in the 1980s from the nuclear black-market network headed by a top Pakistani scientist.
AEA chief Mohamed ElBaradei says Iran has admitted it received an offer from the A.Q. Khan network, including full knowledge of nuclear enrichment technology. But Iran claims it turned down essential parts of the offer, which could have been used to develop nuclear weapons.
IAEA spokesman Mark Gwozdecky says the agency is making progress in understanding Iran's past nuclear activities that were kept secret from the world for almost two decades.
"We are getting co-operation from Pakistan to help us resolve the contamination issue and that relates to trying to match up the fingerprints of what our environmental samples show in Iran and to try and see if we can find matches of those fingerprints elsewhere perhaps from Pakistan or another country," he said.
Mr. Gwozdecky says this is essential in finding out whether Iran's nuclear program is purely peaceful, as Tehran claims.
The International Atomic Energy Agency says Iran is allowing inspectors access to nuclear sites, including one military location.
But it says some information promised by Iran has yet to arrive, and Mr. ElBaradei spoke of Iran's "confidence deficit," because of significant past undeclared nuclear activities.
Diplomats say the International Atomic Energy Agency is not likely to pass a resolution on Iran anytime soon, in order to give more time for negotiations between Tehran and European nations. Iran has agreed to voluntarily suspend its enrichment program and reprocessing activities.
The IAEA chief told diplomats that North Korea's declaration that it has nuclear weapons is of "utmost concern" and has "serious security implications." Diplomats say the IAEA board could adopt a resolution on North Korea later this week, calling for the return of international inspectors expelled from the communist state at the end of 2002.