The U.S. Defense Department has denied a claim by Iran that U.S. spy planes have been flying over that country in an effort to gather intelligence about its nuclear facilities. 

Pentagon spokesman Lawrence DiRita dismissed Iran's claim during a news briefing on Tuesday. 

"I would consider the source and leave it at that,” said Mr. DiRita.  “It's not happening out of this department, and to the best of our knowledge it isn't happening, period."

Last Wednesday, Iran's Intelligence Minister accused the United States of flying spy missions over Iran for a long time.  Referring to reports that Iranians in one region have seen shiny unidentified objects in the sky, the minister said most of them are what he called "American spying equipment."  He also threatened that the aircraft could be shot down by Iranian air defenses.

A few days earlier, the Washington Post quoted unidentified U.S. officials as saying unmanned American spy drone aircraft had been flying over Iran from time to time for the last year, seeking information about its controversial nuclear program.  The report said Iran has not turned on its air defense radar system in response to the flights so as not to reveal its locations.

Iran says its nuclear program is not military, but the United States and other countries, and the International Atomic Energy Agency, have expressed concerns it could be used to develop a nuclear weapon.  There is particular concern about Iran's efforts to enrich uranium, a process which could create fuel for nuclear bombs.

Britain, France and Germany have been offering Iran economic and political incentives to abandon the enrichment program, and have urged the United States to join the process.  But the United States has refused, saying Iran must first abandon any nuclear weapons program before any incentives should be offered.

Still, senior U.S. officials say they favor a diplomatic solution to the dispute.  During his trip to Europe Tuesday, President Bush said the idea that the United States is planning to attack Iran is "ridiculous," but he also said all options are on the table.