US Defense Secretary Donald Rumsfeld said on Sunday he has never authorized military overfights of Iran for intelligence on the country's alleged nuclear program.

Speaking in ABC television's "This Week" program, he said "I checked and I know we had no US aircraft doing what ... Iran was saying."

The defense chief rejected recent US reports which said US surveillance planes have been overflying Iran since April 2004, spying on Iran's nuclear program and probing for weaknesses in its air defense.

The small, pilotless planes penetrated Iranian airspace from US military facilities in Iraq, trying to pick up traces of nuclear activity to gather information that was not accessible by satellites, the Washington Post quoted officials with detailed knowledge of the secret effort as saying in early February.

Rumsfeld said, "What investigations we've been able to undertake have suggested that the charge was false," noting that "it may very well have been Iranian air activity in that country by elements of the government that were not coordinating with other elements of the Iranian government."

When pressed about whether any US intelligence agencies might have organized such flights, Rumsfeld did not rule out the possibility, saying that "I can't speak for intelligence agencies, but not to my knowledge."

Rumsfeld also denied knowing about reports that Iran has protested to the United States about US reconnaissance flights on its territory and that the protest was forwarded to the Pentagon.

The reported spy flights have raised concerns about US military preparations for possible attacks on suspected Iranian nuclear sites.

US officials have declined to rule out a military option, but have indicated they are giving international diplomatic efforts a try first.

Source: Xinhua