WASHINGTON (Reuters) -President Donald Trump's order for the Defense Department to start testing nuclear weapons could lead to billions of dollars' worth of contracts for a handful of specialized companies that dominate the United States' nuclear weapons infrastructure.    

The Trump announcement Wednesday night from South Korea ordered the Department of Defense to "immediately" start testing nuclear weapons, something the United States has not done since 1992.

The U.S. nuclear arsenal consists of land-launched nuclear missiles, nuclear missile-armed submarines and aircraft with nuclear bombs and missiles. It was unclear which portion of the arsenal Trump wanted to test.

COMPANIES IN LINE TO BENEFIT

An investment in nuclear weapons and testing could benefit Honeywell International ( HON ), BWX Technologies ( BWXT ), Chugach Alaska Corp, Jacobs Solutions, Inc. ( J ), Mele Associates, General Atomic Technologies Corporation and others due to their specialization in nuclear test site construction, operations, support and related engineering services, according to Govini, a defense software company.

BWXT works with nuclear materials, while Honeywell ( HON ) runs a key testing site, conducts tests and helps track the U.S. nuclear stockpile.

Mele helps manage parts of the nuclear stockpile while helping make sure nuclear material does not fall into the wrong hands.

"Restarting nuclear weapons testing is going to reverberate in a lot of ways, including by sending a shockwave of government funding to companies in test site construction and engineering support," said Tara Murphy Dougherty, CEO of Govini.

Alongside a new testing program, the U.S. is modernizing its ground-launched intercontinental ballistic missile program, aimed at replacing the aging Minuteman III missiles. 

Northrop Grumman ( NOC ) was awarded a sole-source contract in 2020 to develop the Sentinel, with subcontractors including Lockheed Martin ( LMT ), General Dynamics, Bechtel, Honeywell ( HON ), Aerojet Rocketdyne, and Textron. 

The program, which requires extensive testing while it is being built, represents one of the largest defense modernization efforts in decades.

The plan includes 634 new Sentinel missiles, plus an additional 25 missiles to support development and testing, being procured to replace the aging Minuteman III system deployed in 1970.