WASHINGTON U.S. Senator Elizabeth Warren, a Democrat and frequent merger critic, joined three other lawmakers on Tuesday to urge the Defense Department to thoroughly review defense contractor L3Harris Technologies' $4.7 billion deal for Aerojet Rocketdyne Holdings.

The Defense Department is influential with the antitrust agencies on decisions about approving deals that touch on military issues, and often take too soft an approach, Warren and the other lawmakers wrote.

"Lockheed Martin, Raytheon, and Boeing are all dependent on products that only Aerojet is able to produce, and their operations could be hamstrung by its acquisition," they wrote.

The letter was sent to Defense Secretary Lloyd Austin and William LaPlante, undersecretary of defense for acquisition and sustainment.

In addition to Warren, the letter was signed by Representatives Chris Deluzio, John Garamendi and Mark Pocan. All are Democrats.

The lawmakers said the department had previously conducted what the letter called "flawed merger reviews."

With the Ukraine war driving up demand for missiles and defense systems, Aerojet became an attractive takeover target. L3Harris was formed by the merger of L3 Technologies and Harris Corp in 2019.

The United States has assisted Ukraine with billions of dollars in military aid, including missiles and air defense systems.

Aerojet develops and manufactures liquid and solid rocket propulsion and hypersonic engines for space, defense, civil and commercial applications.

Another customer is the National Aeronautics and Space Administration (NASA), one of Aerojet's main customers, which is pursuing moon and deep space missions.

(Reporting by Diane Bartz; Editing by David Gregorio)