Northrop Grumman Tuesday accused the Pentagon of being "unfair" over the aerospace giant's competition with Boeing for a new mammoth contract to replace the US Air Force's aging aerial tankers.

Northrop charged that the Defense Department gave the company's key pricing information from a previous tanker competition to Boeing while access to comparable pricing data from the rival was denied.

"It is fundamentally unfair, and distorts any new competition, to provide such critical information to only one of the bidders," Northrop vice-president Paul Meyer said in a statement.

He said however that his company would continue to work with the Pentagon "to fully resolve this issue."

The two rival bidders have expressed optimism they could win the contract to build the tankers after the Pentagon reopened the competition last week.

Two previous attempts to award the 35-billion-dollar contract collapsed amid scandal and bitter disputes between the rival bidders.

Northrop remains partnered with Airbus parent firm EADS, the European Aeronautic Defence and Space Company, in the new bid.

"Northrop Grumman continues to be greatly concerned that its pricing information from the previous tanker competition was provided by the government to its competitor, Boeing," Meyer said.

"Access to comparable pricing information from Boeing has thus far been denied by the Pentagon," he said.

Meyer pointed out that "with predominant emphasis placed on price" in the re-competition and with Northrop again proposing its KC-45 refueling tanker, "such competitive pricing information takes on even greater importance."

The Pentagon had said it would use concrete criteria in judging proposals instead of the "confusion" that plagued a failed attempt last year to award a contract.

The politically charged contract for 179 aircraft to replace the aging fleet of mid-air refueling tankers has had a troubled history, marked by acrimony between the aviation giants.

A contract for the tankers was awarded in February 2008 to Northrop and EADS but the deal was withdrawn in July last year after Boeing successfully appealed the decision to the investigative arm of the US Congress — the Government Accountability Office.

The GAO found rival proposals were not evaluated fairly.

In 2004, the Pentagon was forced to drop plans to buy and lease tanker aircraft from Boeing after two senior executives at the firm were convicted in a conflict-of-interest scandal.

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