WASHINGTON – Many lawmakers on Capitol Hill are challenging the administration’s plan to cut back on shipbuilding even as the proposed Pentagon budget would zoom up by $48 billion to $379 billion.

“The trend in shipbuilding worsens in this budget,” Rep. Ike Skelton, top Democrat on the House Armed Services Committee, told Defense Secretary Donald H. Rumsfeld at a hearing Wednesday.

“The request for five new ships again falls well below replacement rates and continues the dangerous trend that will soon bring the United States to a 200-ship Navy – a level totally inadequate for the protection of sea lanes and other American interests,” said Skelton, D-Mo.

Rumsfeld tried to pre-empt some criticism in appearances before the House and Senate Armed Services panels by saying in his opening remarks: “We clearly were not able to fund shipbuilding at replacement rates in 2003, and we must do that in the future.”

The Navy’s four-year defense plan budgets five ships in 2004, seven in 2005, seven in 2006, and 10 in 2007.

Sen. Edward M. Kennedy, D-Mass., said Clinton administration plans called for building 23 new ships from 2003 through 2005, compared with the Bush administration’s proposal for 17.

“Even with your increase in budget, the shipbuilding budget is really rather dramatically lower than it was even in the Clinton program, which had a significantly lower defense budget,” said Kennedy, chairman of the Armed Services Committee’s sea power panel.

President Bush’s defense budget for the year that begins Oct. 1 would spend $8.6 billion on shipbuilding. The five ships would be a reduction from six this year, and Rumsfeld blamed contractor problems, the need to pay for work done previously in which the cost was underestimated, and Navy priorities.

The Navy calculated the cutback wouldn’t endanger the country because the fleet is relatively young, he said.

“A lot of the ships were purchased during the 1980s, and the average age of the Navy, I am told, is at or slightly better than the average age that is expected and targeted,” Rumsfeld told the Senate panel Tuesday.

“We can afford for a year or two to be underbuilding, as long as we recognize that in the out years we simply must get back up to the … seven, eight, nine, 10 levels,” he said. Sticking with five a year would lead to “an unacceptably small Navy.”

The Navy felt it was more important now to correct shortfalls in munitions, spare parts and steaming hours, which the budget fully funds, Rumsfeld said.

The budget also calls for converting four nuclear submarines into vessels that can fire cruise missiles and insert Special Forces into battle, at a cost of $1 billion. Rumsfeld said Wednesday that there would be two, not four, conversions next year.

That work does “not count in ship numbers because while they give us new capabilities, they don’t buy new ships as such,” Rumsfeld said.

His arguments did not assuage all lawmakers.

“Your budget tells me you’re getting complacent about the needs of the U.S. Navy,” Rep. Gene Taylor, D-Miss., told Rumsfeld.

Concerns also came from Republicans.

“There seems to be a pattern in which the department sincerely plans and hopes to increase ship construction rates in future years, but then ends up scaling back the plans when funding runs short,” said Sen. Susan Collins, R-Maine. “My concern is that if we don’t start this year, and instead only proceed with five ships this year, that we’re just going to fall further and further behind.”