Updated

Iran has not been cooperating as openly or quickly as it should to dispel the suspicion it wants to build nuclear weapons, the chief U.N. inspector said Monday as he left for Tehran (search) to apply new pressure on the Islamic regime.

Mohamed ElBaradei (search), director-general of the International Atomic Energy Agency, was slated for talks in Tehran amid indications of continued nuclear cover-ups and signs that even previously reluctant U.S. allies are moving closer to Washington's view that Iran should be penalized.

ElBaradei said he would address two key points with top Iranian officials: The origins of traces of highly enriched uranium (search) found in the country, and details on Iran's advanced P-2 centrifuges — equipment that could be used to enrich uranium for use in a weapon.

"We need to satisfy ourselves that there are no undeclared activities that have taken place in Iran," ElBaradei told reporters before leaving for Tehran.

"I and the international community would like to bring the issue to a conclusion," he said. "It obviously cannot go on forever."

ElBaradei arrived in Tehran early Tuesday.

Vienna-based diplomats familiar with the IAEA's activities in Iran, where experts have been examining nuclear sites and programs for signs of past and present weapons ambitions, said there is lingering doubt about whether Iran is revealing all of its activities.

Iran insists its nuclear program is peaceful and geared only toward producing electricity. The United States and other nations contend it masks a covert effort to build a nuclear weapon.

"At the end of the day, the issue is to really create confidence that this is a program for peaceful purpose," ElBaradei said Monday, calling on the Tehran regime to "turn over a new leaf."

ElBaradei was to arrive in Tehran early Tuesday and return to Vienna on Wednesday after meeting with senior government and Iranian nuclear agency officials.

He said last month's resolution by the IAEA's 35-nation board of governors, which censured Iran for hiding suspicious activities, showed that the board is "getting a little bit impatient and they would like to see progress."

"I sense some slowdown," ElBaradei said. "We have seen some delay in the inspection process ... in getting the information we would like to receive. I would like to make it clear in my visit that restoring and accelerating the speed of cooperation is in the interest of everybody."

On Sunday, Iran denied it has hidden any nuclear facilities by shifting them to easier-to-conceal sites.

Iranian officials were responding to alleged intelligence from the United States and an unnamed country suggesting that within the past year, Iran had moved nuclear enrichment programs to less detectable locations.

ElBaradei said last month that Iran has much to do before the IAEA can declare Tehran's nuclear program peaceful.

Iran's nuclear ambitions first came under international scrutiny last year, when the IAEA discovered that Tehran had not disclosed large-scale efforts to enrich uranium, which can be used in nuclear warheads. Finds of traces of weapons-grade uranium and evidence of suspicious experiments heightened concerns.

Critics say that Iran since has reneged on commitments to win international trust — such as a promise to suspend enrichment — as IAEA inspectors have discovered new evidence of past experiments that could be used to develop weapons.

"There is a growing feeling that the Iranians are playing games instead of honoring pledges of full disclosure," one diplomat said Monday, speaking on condition of anonymity.

Adding to the skepticism was Iran's announcement last month that it inaugurated a uranium conversion facility in Isfahan, 155 miles south of Tehran, to process uranium ore into gas — a crucial step before uranium enrichment.

Iran insists the move does not contravene its pledge to suspend enrichment. But Britain, France and Germany — who have blunted past U.S. attempts to come down hard on Iran — were critical. They said the Isfahan plant sent the wrong signal.

Last year, the three secured Iran's agreement to suspend enrichment and cooperate with the IAEA in exchange for promised access to western technology. They have stymied U.S. attempts to have Tehran brought before the U.N. Security Council for allegedly violating the Nuclear Nonproliferation Treaty.