WASHINGTON: A report by a nonpartisan congressional research group says sharp increases in the proposed budget to build a "bunker buster" nuclear bomb raises questions about whether the controversial programme is only a study , as US officials have contended.

Last year, Defence Secretary Donald H. Rumsfeld said the effort was "a study. It is nothing more and nothing less." But a report from the Congressional Research Service said the five- year, $485-million-dollar budget proposal "seems to cast serious doubt on assertions that the Robust Nuclear Earth Penetrator is only a study."

The report noted that the programme, budgeted for $7.5 million in the current fiscal year, would grow to $27.6 million in fiscal 2005, under the budget proposal. Spending would rise to a peak of $128 million in fiscal 2008, followed by $88 million in 2009.

By the end of that period, according to this schedule, the Energy Department would have a bomb design and would develop a process for building it. Advocates say a nuclear bomb with a special hardened shell could burrow underground before exploding and destroy buried structures that conceal arsenals and command centres.

Countries around the world, including North Korea and several nations in the Middle East, have built extensive underground military facilities, hoping to elude the long reach of American conventional military power.

Advocates argue such a weapon would enable the United States to deter future underground projects. Foes argue that its use could devastate nearby populations and set off a new nuclear arms race.

The Congressional Research Service report, issued to Congress on Monday, was not intended for public distribution. But the Federation of American Scientists, an arms control advocacy group, obtained a copy and displayed the report on its Web site.

Brian Wilkes, a spokesman for the Energy Department's National Nuclear Security Administration, insisted on Wednesday that policy- makers have not decided to build the bomb; rather, he said, the budget figures were developed only to fulfil the congressional requirement to have a five-year budget plan.

"This is a placeholder budget," Wilkes said. "We have to plan for every contingency." Steven Aftergood, of the Federation of American Scientists, said that the government does not propose five-year budgets for every research programme that might be approved for development.

"If they had placeholders for every funding scenario, they'd have to request an infinite amount of money," Aftergood said. "This is an expression of intent to move ahead with an expanded programme; I think that's the only way to understand it."

Congressional opponents of the programme have tried several times to cut funding and restrict its pace. Last year, opponents succeeded in requiring the administration to win special congressional approval to move from research into the development phase of the programme.

But one opponent, Republican Ellen O. Tauscher, said the budget figures showed "they've been slow-walking us on the details, but fast-tracking money in order to go full steam ahead if they find themselves with a Republican house and senate" after the November elections. -Dawn/The LAT-WP News Service (c) The Los Angeles Times.