WASHINGTON — The U.S. Navy is preparing to sign a contract with General Dynamics Electric Boat and subcontractor Huntington Ingalls Industries for the next tranche of Virginia-class submarines, according to budget documents submitted to Congress this week.

The 10-ship contract, which will include nine of the 84-foot Virginia Payload Module upgrades, is planned for April, the documents say. The VPM is designed to triple the Tomahawk cruise missile capacity of the Virginia-class subs, a move designed to offset the pending retirement of the Ohio-class guided-missile subs, which have a 154-Tomahawk capacity. Each Virginia Payload Module sub will have a 40-Tomahawk loadout.

The first Virginia Payload Module ship, SSN-803, will be awarded as part of the block buy and is slated for a 2025 delivery, the documents say.

The contract is sure to be the largest submarine contract since 2014, when the Navy signed a 10-sub, $17.6 billion contract with Electric Boat and HII for the Block IV Virginia subs. The first of the Block IV ships, the attack submarine Vermont, is slated to be delivered in October, according to budget materials, with the final Block IV slated to be delivered in 2023.

The contract could still face delays, however. Last year’s budget materials listed the contract date for the Block V boats as October 2018, which has come and gone.

The Navy is pushing to boost attack submarine production ahead of an expected dip in attack boat numbers. The Navy expects to drop from 52 to 42 attack boats by the late 2020s, a move that prompted the Navy this year to add a third SSN to the budget and bump the start of LPD Flight II construction.

The Navy’s top officer said the move is meant to get the Navy closer to its required SSN levels.

“We’re much farther away from our war-fighting requirement in SSNs than we are in amphibs," Chief of Naval Operations Adm. John Richardson said at a March 13 roundtable. “So that was just a war-fighting priority.”

Richardson also sounded a cautious note on service-life extensions for Los Angeles-class attack submarines, saying the service is looking at each sub individually.

“It’s kind of a case-by-case basis,” Richardson said. "These submarines, the usage over their life is varying. You have to do it hull by hull. Overall, though, I’m pretty optimistic that that’s going to help us meet our requirements and attack submarine numbers.”

Correction: An earlier version of this story misstated the award date for the first Virginia Payload Module ship. A change to the story also clarifies the number of VPMs expected in the block buy.