Boeing on Tuesday said it had carefully studied both its 767 and larger 777 aircraft for use in a new US aerial refueling competition, but would not decide which plane to bid until the Pentagon released the terms of the competition.

Dave Bowman, Boeing vice president and general manager of tanker programs, said the company had done "a lot of work" on possible tanker variants since the Pentagon cancelled a USD$35 billion contract with Northrop Grumman and its partner, Airbus parent EADS, last year.

Bowman said Boeing's commercial wing was cooperating closely on the tanker proposal, and was ready to support either the 767 or 777, depending on what Boeing decided to offer.

"Whether it's a 767 base or a 777 base or something in between, they're 100 percent on board," Bowman told reporters at the Paris Air Show.

Northrop and Boeing executives have used the Paris Air Show to breathe new life into a competition that will soon enter a third round.

Boeing had considered the 777 as a possible tanker offering during the last competition, but opted for the 767 because it was convinced the Air Force did not want such a large aircraft.

After Northrop and EADS won with their A330, Boeing officials began to question if they should have offered the 777 after all. But analysts said the commercial side of the house was not that supportive last time.

Bowman declined to give any details of Boeing's possible plans, but said every possible variant had been studied.

He acknowledged that Boeing could be at a disadvantage if the Air Force opted for a large tanker, and wanted it done quickly.

EADS, already building an A330-based tanker for Australia, would have a leg up in that case, he said, but he noted that it was unclear what the Air Force's priorities would be.

The Air Force's first bid to replace its fleet of KC-135 refueling aircraft centered on a lease/buy deal with Boeing for 1,000 767s, but that collapsed in 2004 amid a major procurement scandal that sent a former Air Force official and Boeing's former chief financial officer to prison.

Northrop won the second competition, which was carefully monitored by Pentagon officials, but government auditors still upheld 8 of over 100 protest points raised by Boeing in its protest.

Lawmakers weighed in, as did the companies with scores of full-page newspaper advertisements, elevating the issue to such an extent that Defense Secretary Robert Gates ultimately said the only solution was to start over.

The Pentagon is expected to release a draft request for proposals soon after vetting it with concerned lawmakers.

Analysts say both sides may file protests once those draft terms are finalized, if they find any evidence that the rules are tipping the competition toward one competitor or another.

Northrop CEO Ron Sugar, asked if the two sides would form a gentleman's agreement not to ratchet up the rhetoric this time around, said the two companies often collaborated as well as competed.

In this case, however, he said, "We don't collaborate on competitions."

Jim Albaugh, who heads Boeing's defense sector, said the stakes were clearly high, and Boeing would do all it could to win this time around.

"I'd just as soon not lose that program a second time," he told reporters Sunday ahead of the Paris air show.