General Dynamics Corp. announced yesterday that it will lay off up to 2,400 of its submarine workers in Connecticut and Rhode Island starting early next year and warned that thousands more jobs could be lost if the shipyards do not get more work.

Falls Church-based General Dynamics said the layoffs, about 20 percent of the 11,400-person workforce, were necessary because the company had not received expected contracts to repair submarines and had nearly finished other projects. The company is also attempting to cut the cost of building the Navy's Virginia class nuclear submarine, which hunts other subs and can attack surface targets, to $2 billion each from $2.5 billion.

"It's important for us all to bear in mind that these reductions are the result of pressure of the Navy's shipbuilding budget," John P. Casey, president of the facilities known together as Electric Boat Corp., said in a statement. "Everybody affected by the layoffs deserves to be treated with dignity and respect through their last day at Electric Boat."

The actual number of layoffs could be 500 fewer if enough positions are eliminated through attrition and retirements, said company spokesman Robert Hamilton.

If conditions do not change, an additional 4,000 jobs at the company's submarine facilities could be lost, Hamilton said. Based on current orders, General Dynamics has enough work to build submarines until 2014, he said.

General Dynamics and Northrop Grumman Corp. of Los Angeles are the Navy's last remaining makers of submarines and share the work, with each company building half of each ship. For years, the industry has advocated building more submarines each year, two instead of one. But such plans have been repeatedly delayed because of budget constraints, industry officials have said.

The layoffs are "a sign of the times that we're in," said Cynthia L. Brown, president of the American Shipbuilding Association, an industry lobbying group. Laid-off workers will be expensive to replace if the Navy decides to begin development of a new type of submarine later, she said.

Earlier this year the Pentagon proposed cutting more than $5 billion from the Virginia program.

Northrop has no plans for layoffs, said company spokesman Brandon R. "Randy" Belote.