A confrontation is brewing between the United States and Iran, with the Shiite cleric country vowing to continue to put limits on U.N. weapons inspectors and the Bush administration urging them to do more about Iran's nuclear program. The International Atomic Energy Agency has said it expected Iran "to grant the agency all access deemed necessary" to defuse suspicions Tehran is operating a clandestine nuclear weapons program. The U.S. President Bush, who has called Iran and North Korea members of an axis of evil, has said he and other world leaders will not tolerate nuclear weapons in Iran. In London, a senior U.S. official said that while military action against Iran to stop it developing nuclear weapons is far from the thoughts of Washington, it remains an option as a last resort. John Bolton, undersecretary of state for arms control and international security, insisted Iran can not be allowed to develop a weapons capability that could destabilize the whole region. Iran's state television said the head of Iran's Atomic Energy Organization, Gholamreza Aghazadeh, would not permit environmental sampling at "some locations." It did not name the locations. The refusal indicated a hardening of attitude toward the U.N. nuclear watchdog group. "We've had no problem concerning environmental samples, but we've been telling the IAEA that this location is not a nuclear location, so that if you want to take environmental samples, this is outside the framework of the protocol, "Aghazadeh said. He did not identify the location. "If we accept to operate outside the framework of the protocol, it will have no ending ... and tomorrow ten other locations may be named," Aghazadeh added. Inspectors were turned away from a site at Kalaye, west Tehran, earlier this month after they came to take environmental samples. The Iranians have allegedly tested centrifuges at the Kalaye site. A Western diplomat familiar with the dispute said Aghazadeh appeared to be referring to the Kalaye site. Tehran would be obligated to open the site to environmental sampling by IAEA experts only if it signed an additional protocol - something the U.N. agency urged Iran to do at its board meeting in Vienna, Austria, this week. Judging by Aghazadeh's reaction, Iran is turning a cold shoulder to this request. The diplomat, who spoke on condition of anonymity, said the protocol was crucial - "to put the pieces of a nuclear puzzle of a country together, it is not enough to go to declared nuclear sites. IAEA spokeswoman Melissa Fleming said the agency had no comment on the report. Iran says its nuclear program is designed solely to produce electrical energy, particularly after its oil wells run dry. IAEA inspectors are expected to return to Iran next month, and IAEA chief Mohamed ElBaradei said he expects Iran's cooperation in what will be the first test of Iran's willingness to comply. "I trust, I expect, that Iran will enable us to do all that we need to do," ElBaradei said during this week's board meeting. ElBaradei has asked Iran to permit monitors to take environmental samples at a location where the country has allegedly enriched uranium - a step in producing nuclear weapons. On Thursday, the IAEA challenged Iran to prove it does not have a nuclear weapons program, but rejected Washington's effort to bring the matter before the U.N. Security Council. The United States suspects Iran is trying to build a nuclear bomb and Washington's delegation to the IAEA had pushed for the agency to declare Iran in violation of the Nuclear Nonproliferation Treaty. Iran denies it is seeking a nuclear bomb and says its nuclear program is designed to produce energy, particularly after its oil reserves run dry. At its board meeting, the IAEA also urged Iran to stop enriching nuclear fuel and to allow greater access to its nuclear facilities. Aghazadeh did not respond Friday to the IAEA demand for a cessation of uranium enrichment. **PHOTO CAPITON*** Iran's representative at the IAEA meeting Ali Selehi (R) answers journalists' questions in Vienna. (AFP/File/Dean Calma)