In Washington, Rumsfeld said at a hearing before the Senate Armed Services Committee: “Our policy historically has been generally that we will not foreclose the possible use of nuclear weapons if attacked.”

He said the United States would not “rule out various options,” but said “those weapons ... have not been fired in anger since 1945.”

Rumsfeld’s comments came during questioning by Sen. Edward Kennedy, a Massachusetts Democrat, who expressed alarm that the Bush administration may be considering lowering the threshold for possible use of nuclear weapons.

President George W. Bush, meanwhile, steeled U.S. Navy sailors for possible war with Iraq and urged the United Nations to have the “backbone and courage” to force Baghdad to disarm.

“I believe, when it’s all said and done, free nations will not allow the United Nations to fade into history as an ineffective, irrelevant, debating society,” Bush told some 4,000 troops at Naval Station Mayport in Florida.

U.S. defense officials said yesterday small units of elite U.S. Special Operations forces are busily operating inside several areas of Iraq to lay the foundation for a possible invasion of the country.