President Bush has dropped the equivalent of 100,000 dirty bombs on America

Nevada Senator Harry Reid

Opponents are expected to formally object to Mr Bush's order, leaving Congress to decide by the majority vote of both houses.

The site of Yucca Mountain, some 150 kilometres (90 miles) from Las Vegas, was singled out 15 years ago as America's potential nuclear waste repository.

Under government plans, more than 70,000 metric tons of radioactive material from America's 103 nuclear power plants would be stored deep inside the mountain for about 10,000 years.

US officials say that keeping nuclear waste at a single site is crucial for national security since the 11 September attacks on New York and Washington, which raised concern about guarding America's dangerous material.

Critics' fears

But the site's critics are concerned that radioactive material may leak into surrounding ground, posing health risks. They are also worried about the risks involved in transporting nuclear waste over long distances.

I reached the conclusions that technically and scientifically the Yucca Mountain site is fully suitable

US Energy Secretary Spencer Abraham

Nevada Senator Harry Reid criticised Mr Bush's decision, saying the president "betrayed our trust" by breaking a campaign promise not to go ahead with the plan without sound scientific study.

Senator Reid said the plan would lead to the equivalent of 100,000 nuclear waste-laden trucks moving through 43 states from existing storage sites to Nevada.

"President Bush has dropped the equivalent of 100,000 dirty bombs on America," he said.

If the site is approved by Congress, the Nuclear Regulatory Commission must also approve a license for the site, which would likely face legal challenges and could delay the plan for up to two years.

The US Energy Department says Yucca Mountain's advantages are that it is geologically stable and isolated on federally controlled land.

It says the repository would be housed about 300 metres (1,000 feet) underground, and located further from any metropolitan area than most of the less secure, temporary nuclear waste storage sites that exist today.

"We should consolidate the nuclear wastes to enhance protection against terrorist attacks by moving them to one underground location that is far from population centres," the Energy Department has said.

In a letter to President Bush accompanying the recommendation, Energy Secretary Spencer Abraham said he was convinced the Yucca Mountain site was suitable.

"After months of study based on scientific and technical research unique in its scope and depth, and after reviewing the result of a public review process that went well beyond the requirements of law, I reached the conclusions that technically and scientifically the Yucca Mountain site is fully suitable," he said.