General Dynamics NASSCO has received a contract modification valued at up to $1.6bn from the US Navy to construct the sixth and seventh expeditionary sea base (ESB) ships.

The contract also includes an option for ESB 8, the eighth ship under the programme.

The fixed-price incentive modification contract is for the design and construction of the two ships and has a base value of $1.08bn. If the option for the eighth ESB is exercised, the contract value would reach $1.63bn.

General Dynamics NASSCO president Kevin Graney said: “We are pleased to be building ESB 6 and 7 for our navy. ESBs have proven to be affordable and flexible, and as the fleet has gained experience with the platform, we have worked with the navy and marines to develop even more capabilities and mission sets.”

The navy has a practice of naming the ESB ships after popular names or places of significance to US Marines.

The vessels form part of the US Navy’s airborne mine countermeasures mission.

“NASSCO will start work on the two ESBs in the first quarter of next year, with completion expected in the second quarter of 2023.”

ESBs have a large helicopter flight deck and can carry up to 250 personnel. The ship is also designed to support special mission and Marine Corps task-organised units.

NASSCO will start work on the two ESBs in the first quarter of next year, with completion expected in the second quarter of 2023.

The company won a $744m contract modification in May 2011 to fund the construction of the first two vessels under the Expeditionary Transfer Dock (ESD) programme, formerly known as the Mobile Landing Platform (MLP) programme.

In May 2013, NASSCO delivered USNS Montford Point, the first ship of the class. USNS John Glenn, the second ship in the ESD programme, was delivered in the following year.

The navy asked the firm to build three more vessels under the programme. These three ships, the USS Lewis B Puller, USNS Hershel ‘Woody’ Williams and the Miguel Keith, were configured as ESBs.

Miguel Keith is anticipated to be delivered to the navy in the fourth quarter of this year.