The U-S State Department is accusing Iran of trying to hide parts of a new nuclear facility, and says the project appears to be part of a secret effort to make nuclear weapons in violation of international treaties.
State Department spokesman Richard Boucher says Iran is trying to camouflage the true purpose of a facility near the central town of Natanz by burying a suspected uranium enrichment plant underground.
He said commercial satellite imagery shows part of the plant is already being covered with earth.
Mr. Boucher also said Tehran has repeatedly rejected requests from the U-N nuclear watchdog agency to inspect the Natanz facility and another nearby project. U-N inspectors are now set to visit the sites in February.
Iran says its nuclear program is aimed at peaceful civilian purposes, and officials have insisted the country does not have any hidden nuclear activities.
A White House spokesman (Ari Fleischer) also expressed Washington's concerns about the Iranian facilities, and questioned the need for nuclear power in a country with oil and natural gas reserves as large as Iran's.
The independent Washington-based Institute for Science and International Security also has expressed worry about the facilities. The group says the sites appear related to the production of enriched uranium and heavy water -- two so-called dual use materials that could be used in a civil nuclear program or in the production of banned weapons.
Thursday, un-named U-S officials told the Cable News Network they also believe the two suspect sites include refineries that could produce weapons-grade enriched uranium.