Northrop Grumman said the U.S. government had given rival Boeing a fundamentally unfair edge in their renewed battle for a potential $50 billion contract to build aerial tankers.

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, Paul Meyer, a Northrop vice president, said in a statement.

In what could set the stage for a protest even before the new competition gets under way, Meyer said access to comparable pricing information from Boeing had so far been denied by the Pentagon.

With predominant emphasis placed on price in this tanker re-competition and Northrop Grumman again proposing its KC-45 refueling tanker, such competitive pricing information takes on even greater importance, he said.

It is fundamentally unfair, and distorts any new competition, to provide such critical information to only one of the bidders, Meyer said.

He said Northrop Grumman, which remains partnered with Airbus parent EADS for the new competition, would continue to work to fully resolve this issue.

A year ago, the Pentagon scrapped a previous tanker deal awarded to Northrop and Europe's EADS after the U.S. Government Accountability Office, the audit arm of Congress, upheld a protest by Boeing.

The GAO found the Air Force had failed to follow its own rules in evaluating the bids. As part of the fallout from the protest, Boeing received some pricing information, although Pentagon officials sought last week to play down its significance.

Northrop Grumman, prime contractor for the trans-Atlantic team, said it was continuing to analyze the U.S. Air Force's draft bidding rules that were released last week.

It looked forward to discussions with the Air Force to better understand the request, Meyer said.

On Friday, Boeing said it was deciding whether to stick with its modified 767 tanker, which lost the previous, canceled competition to an Airbus A330-based tanker, or go with a larger 777-based tanker -- or offer both.

A senior military officer, at a Pentagon background briefing on Friday, estimated the program could be worth as much as $50 billion, up from previous estimates that put its value at $35 billion over 15 years.

The companies have 60 days to comment on the Air Force's draft request for proposals before final bidding specifications are released. (Reporting by Jim Wolf; editing by Tim Dobbyn)