Boeing Co., seeking to win the reopened $35 billion U.S. Air Force tanker competition, said it may consider dropping out of the race unless the Pentagon allows the company up to six months to prepare its proposal.

The Air Force's draft proposal announced Aug. 6 gives priority to "fuel capacity and offload, and our 767-200 doesn't fill that bill," said Daniel Beck, a spokesman for Chicago-based Boeing. Boeing would have to conduct multiple studies "to come up with a proposal that meets this requirement."

In the last round of the competition, Boeing and Northrop Grumman Corp., which won the contract in February, had about "seven to eight months" to submit bids after a draft proposal was announced, Beck said. The competition was reopened after a successful protest by Boeing.

"We are asking for six months to put together a meaningful proposal" for the second round, Beck said.

Pentagon officials have said they may allow the competitors 45 days to respond to the new bid request, expected to be announced next week.

A second competition for the tankers follows a Government Accountability Office decision on June 19 to uphold a protest by Boeing, saying that the Air Force made "significant errors" in awarding the contract to Northrop.

In the last round of competition that began in January 2007, Los Angeles-based Northrop and its partner Airbus SAS parent European Aeronautic, Defence & Space Co. won the 179-plane contract using an entry modeled after the Airbus A330 commercial jetliner. Chicago-based Boeing, which has supplied Air Force refueling tankers for more than a half-century, based its bid on a modified 767 commercial plane.

The possibility that Boeing may pull out of the competition was reported earlier by the Wall Street Journal.