WASHINGTON (Reuters) - The U.S. Navy is expected to announce this week who will build its next-generation carrier-based stealth fighter - a program worth hundreds of billions over its lifetime and a key part of plans to confront China, people familiar with the decision said.

The F/A-XX program is one of several advanced capabilities the U.S. military is developing to counter China's growing assertiveness in the Indo-Pacific region. The contract would be worth single-digit billions of dollars in the short term, and potentially hundreds of billions over the decades it is expected to run.

The Navy will choose one winner for the engineering and manufacturing development (EMD) phase - a significant milestone for the F/A-XX, which is meant to replace the Navy's F/A-18E/F Super Hornet fleet.

The new jet is expected to feature advanced stealth capabilities, improved range and endurance, and the ability to integrate with both uncrewed combat aircraft and the Navy's carrier-based air defense systems.

The U.S. Navy did not respond to a request for comment. The new Secretary of the Navy, John Phelan, was confirmed on Monday.

The competition has been intense, with Boeing Co ( BA ), Lockheed Martin ( LMT ), and Northrop Grumman Corp ( NOC ) submitting detailed proposals and prototypes for evaluation.

Boeing ( BA ), hit hard by a recent labor strike, engineering layoffs, problems with its Starliner capsule and the troubled KC-46 tanker program, got a recent shot in the arm when it won the Air Force's F-47 contract. It also produces the MQ-25 carrier-based uncrewed refueling aircraft.

Taking on two fighter jet programs may offer economies of scale if the company can make larger purchases of raw materials and share technology between the aircraft.

Northrop Grumman ( NOC ) has a strong track record of producing innovative aircraft, including the B-2 and B-21 stealth bombers.

Lockheed Martin ( LMT ) was initially seen as a strong contender, but the company struggled to meet the Navy's specific requirements, including the need for a more advanced radar system and improved carrier landing capabilities. Reuters reported on March 4 that Lockheed had been eliminated from the competition, but the Navy has not made a formal announcement.

The first production jets are expected to enter service in the 2030s, while F/A-18s are expected to remain in service into the 2040s.