Northrop Grumman Shipbuilding in Pascagoula has been awarded a $213.8 million contract modification to buy materials for a 10th amphibious transport dock ship.

Northrop officials said Wednesday that the construction contract is expected to be awarded in mid-2010.

The contract will allow Northrop to buy materials and major equipment, such as main engines and diesel generators, in anticipation of the construction contract.

The San Antonio-class ships are built to deploy the combat and support elements of Marine Expeditionary Units and Brigades.

The ships are 684 feet long by 105 feet wide and can carry up to 800 troops.