Vienna, Austria ? Ahead of a key trip to Tehran, the chief U.N. nuclear monitor urged Iran on Monday to come clean on suspect programs that could be used to make atomic weapons.

Mohamed ElBaradei, who heads the International Atomic Energy Agency, told The Associated Press that only full cooperation can dispel international skepticism about the country’s nuclear ambitions.

Iran needs “to give us additional authority for the international community to be fully satisfied that the program is completely dedicated to peaceful purposes,” said ElBaradei, who is scheduled to meet with President Mohammad Khatami and other top officials starting Wednesday.

The United States has been at the forefront of accusations that Iran is running a clandestine nuclear weapons program. President Bush — who labeled Iran part of the “Axis of Evil,” along with Iraq and North Korea — warned last month that Iran must keep its promise not to develop nuclear weapons. If the Iranians don’t, “we will deal with that,” Bush said.

Iran denies it wants nuclear weapons, and it has already let the International Atomic Energy Agency inspect parts of its programs. But ElBaradei, who heads the Vienna-based agency, wants Iran to let it make more intrusive checks.

ElBaradei is seeking permission to conduct environmental sampling at one site to see whether suspect radioactive material was used. Diplomats familiar with his itinerary said he would seek a commitment from Tehran to hold off activities involving materials and technologies that can be used to make nuclear weapons until all concerns are laid to rest.

These include the testing of centrifuges used to enrich nuclear fuel, the production of metalized uranium, and the construction of a heavy water facility being built at the central Iranian town of Arak.

Some of these technologies and materials can be used either for peaceful or military purposes, underscoring the need for Iran to be more transparent, ElBaradei said.