WASHINGTON (Reuters) - The Pentagon will pay about 4 percent less for each new Lockheed Martin Corp F-35A fighter jet when it signs a deal worth $3.8 billion with the No. 1 U.S. defense contractor on Friday, according to sources familiar with the deal.

The cost of each conventional takeoff and landing jet in the fifth production contract will be around $107 million, excluding the engine, said the sources, who were not authorized to speak publicly. That compares to a price of $111.6 million in the fourth contract with Lockheed.

The Pentagon is negotiating a separate agreement with Pratt & Whitney, a unit of United Technologies Corp , for the engines that will power the new warplanes. Pentagon officials hope to conclude that agreement by the end of the year as well.

(Reporting By Andrea Shalal-Esa; Editing by Leslie Adler)