Groton — Electric Boat announced Thursday it has been awarded a $313.9 million modification of its contract to build Columbia-class submarines for the Navy.

The modification will support submarine industrial base development and expansion for construction of the Columbia-class fleet of ballistic missile submarines as well as additional support for manufacturing, procurement and delivery efforts for United Kingdom Strategic Weapon Support System kits, EB said in a news release.

“Ballistic-missile submarines are the critical, survivable leg of our nation’s nuclear arsenal and Columbia is the Navy’s top acquisition priority,” Kevin Graney, EB’s president, said. “We are grateful for the steadfast trust and support the Navy and Congress have in Electric Boat as we continue the work we began 15 years ago to deliver Columbia and the next 60 years of deterrence for our nation.”

EB said it will continue to work with its vendors and subcontractors to optimize efforts to ramp up production capability and support the increased demand associated with the Columbia program.

At 560 feet long with a displacement of nearly 21,000 tons, the submarines of the Columbia class will be the largest ever built by the United States. The Columbia will have a life-of the-ship fuel core that will power the submarine for its entire service life, eliminating the need for a mid-service refueling and increasing the time the ship can spend on deployment.

EB will deliver the lead ship in the class to the Navy in 2027.