WASHINGTON – New England lawmakers released a detailed defense of Portsmouth Naval Shipyard on Tuesday, telling Defense Secretary Donald Rumsfeld that the base plays a critical national security role and should be kept open.

The shipyard, located in Kittery, Maine, is considered one of many potential targets in the next round of military base closings that the Pentagon is expected to announce next year.

But in a memo to Rumsfeld, 10 Senate and House members from New Hampshire, Massachusetts and Maine said the shipyard is the country’s most efficient and least costly facility for submarine overhaul and maintenance.

In laying out their case for the base, the lawmakers said it is the only shipyard with unobstructed access to the open ocean, delivers submarine overhauls ahead of schedule, is in a very secure location, and has the space to accommodate more personnel and duties.

They also noted that it has a significant economic impact on more than 38 communities across the region, employs about 4,600 civilians and has an annual payroll of nearly $300 million.

“Portsmouth plays a critical role in our national defense infrastructure now, and must be allowed to do so in the future,” the lawmakers said.

The Pentagon is scheduled to recommend its fifth round of base closings next May and the military services must send their list of suggested savings to Rumsfeld by the end of this year.