Northrop Grumman Corp. is turning to one of its biggest competitors for help staying on schedule in building a warship for the U.S. Navy.

The defense contractor announced Monday that it has awarded a contract to General Dynamics’ Bath Iron Works in Maine for the construction of “upper wing units” for an amphibious transport dock ship, said Northrop spokesman Bill Glenn.

While the companies often compete for military contracts they have worked together on huge projects over the years. Officials say the latest collaboration will benefit both companies and the customer — the Navy.

Northrop Grumman’s Shipbuilding sector is the prime contractor for the San Antonio class ships, also known as the LPD 17 class ships. The ships, which are designed to launch 14 Marine aircraft, are being constructed at Northrop’s facilities in Pascagoula and Gulfport on the Mississippi Gulf Coast and in New Orleans.

“This subcontract helps maintain a healthy industrial base and continues the collaboration between the two largest shipbuilders in the country,” Irwin F. Edenzon, vice president and general manager for Northrop Grumman Shipbuilding, Gulf Coast, said in a statement. “Bath has manufacturing capacity at the right time to provide what we need. It’s the right thing to do for the program and our customer.”

Bath Iron Works will build units for portions of the flight deck and other parts of the vessel. Glenn said the units built by Bath Iron will be shipped by barge to Northrop’s Pascagoula shipyard.

“Obviously, we’re very pleased to have this opportunity and having this work at this time will help us in our efforts to further stabilize our near term work load,” said Bath spokesman Jim DeMartini.

DeMartini said Bath Iron Works had been looking for projects to fill an expected lull as it winds down the DDG 51 class shipbuilding program and begins work on the Navy’s next generation surface combatant, DDG 1000 Zumwalt class.

“Our relationship with Northrop Grumman Shipbuilding extends back many, many years and working together with NGS to support our Navy customer in one way or another has been a constant part of that relationship,” DeMartini said. “As the Navy’s need for ships continues to evolve, so must our business practices evolve to meet those changing needs.”

Bath will be providing units for the USS Arlington, which will be the eighth LPD 17 class ship built by Northrop Grumman, Glenn said. Northrop delivered the first, the USS San Antonio, to the Navy in 2005. There are plans to build one more and the Navy has considered asking for a 10th.

The Arlington is one of three LPD 17 class vessels that will be named in honor the people killed in the Sept. 11, 2001, terrorist attacks, Glenn said. The Arlington is named for the attack on the Pentagon.

The ship should be completed in the spring of 2009 and delivered in the third quarter of 2011, Glenn said. He would not say how much Bath is being paid for the work.

“This is all about keeping a commitment to our customer,” he said. “It’s a situation that helps both companies and it demonstrates how industry can work together to help stabilize the shipbuilding industrial base.”