VIENNA - The head of the International Atomic Energy Agency (IAEA) is flying to Iran this week to discuss a controversial nuclear program that is causing increased concern. The atomic energy agency's chief, Mohamed El Baradei, is expected to probe Iran's commitment to dispelling suspicions that it is running a nuclear weapons program when he meets top officials Tuesday in Tehran.

"Dr. El Baradei is going for the fourth time to Iran in the past 14 months, once again to discuss all the outstanding issues in our verification program," said IAEA spokesman Mark Gwozdecky, who is accompanying Mr. El Baradei. "The trip is a one-day trip. We will see what happens."

The visit comes amid reports about continued nuclear cover-ups and indications that more countries are moving closer to the U.S. view that Iran has a nuclear weapons development program under way. A Vienna-based Iranian diplomat, speaking on the condition of anonymity, said this was speculation and insisted that IAEA inspectors had free access to visit all nuclear locations in Iran.

Iran denies allegations that it is moving nuclear facilities to smaller sites hidden from the atomic-energy agency's inspectors. But Mr. El Bardei said last month that Iran was for years in breach of its international nuclear obligations and that Tehran has yet to convince the international community that its program is purely peaceful.

The IAEA is still looking into the origins of weapons-grade uranium found at sites in Iran and wants to know more about nuclear experiments conducted by scientists that could be part of a weapons program. Britain, France, and Germany are becoming increasingly impatient with Tehran, saying it is sending the wrong signals by starting a uranium conversion facility. Last year, the three nations secured Iran's agreement to suspend uranium enrichment and to cooperate with the IAEA in return for access to western technology.

The United States, Australia, and Canada support tougher action on Iran and are looking for European backing.