WASHINGTON, Dec. 10 (Xinhua) -- U.S. high-tech manufacturer General Dynamics (GD) announced on Monday that its subsidiary has been awarded a 346.5 million U.S. dollar contract modification to improve U.S. Navy nuclear-powered submarines.

Under the contract modification, GD said its subsidiary Electric Boat would "undertake development studies and other work related to Virginia-class submarine design improvements."

GD said its subsidiary would evaluate new technologies in newly built Virginia-class submarines, adding that the contract was initially awarded in 2016, with a potential value of 1.3 billion U.S. dollars through September 2019.

The Connecticut-based Electric Boat is one of the two builders of the highly classified Virginia-class submarines. The other builder of the submarine is Newport News Shipbuilding in the state of Virginia.

According to the U.S. Navy, the Virginia-class submarine is 115 meters long, with a 10.3-meter beam, and its nuclear-powered propulsion system can allow it to travel at a speed over 25 knots or 46 km/h.

With a displacement of about 7,800 tonnes, the sub is manned by about 130 soldiers.

The U.S. Navy sees Virginia-class submarine as a high-tech warship to fight against enemy submarines and ships, launch cruise missiles at ground targets and deploy special forces at hostile coasts. So far, 16 Virginia-class submarines have already been in service.