WASHINGTON (Reuters) - Pratt & Whitney, a unit of United Technologies Corp, on Wednesday responded to sharp criticism from the Pentagon's F-35 program chief, saying it had invested heavily to cut the cost of the plane's engine and was shouldering more risk than usual.

"Despite numerous cuts in the F-35 acquisition plan, Pratt & Whitney has maintained a long-term view and demonstrated our commitment by investing more than $50 million dollars of our own funds and taking on risk ahead of contract schedule to prevent the program from experiencing delays," company spokesman Matthew Bates said in a statement.

He said the company had offered to cover 100 percent of cost overrun risk for a fifth batch of engines, a year ahead of the government's plan, a step he described as "highly unusual" at such an early stage of a new weapons program.

He said the company had also invested heavily to cut the cost of the engine by 40 percent since delivery of the first production engine for the new warplane.

(Reporting By Andrea Shalal-Esa; Editing by Gary Hill)