Mumbai: Boeing has won the fight against competition after US defence secretary Robert Gates canceled a $35 billion air tanker bid that pitted Northrop Grumman Corp and Boeing Co, saying the contest had become too emotional and complex to be decided before the Bush administration leaves office in January.

In February, Northrop Grumman Corp and its European partner Airbus won the bid that involves replacing the more than 500 Eisenhower-age airborne tankers.

But, in July, the successful bidders were forced to give up the contract after rival Boeing Co filed a successful protest with the Government Accountability Office and the bid was reopened. Boeing, however, sought six additional months to prepare a revised bid.

Boeing had originally offered to convert a 767 into a refuelling tanker that the Air Force deemed too small.

The Pentagon's cancellation of the bid for building the next-generation aerial-refueling planes places the defence procurement now under a new president.

The next administration will have full flexibility regarding the requirements, evaluation criteria and budget decisions involved in the competition, the Pentagon said in a statement.

''It is my judgment that in the time remaining to us, we can no longer complete a competition that would be viewed as fair and objective in this highly charged environment,'' said defense secretary Robert Gates in a statement.

Democrats, widely expected to take the presidency in November, have provided strong support for the manufacturer.

''We are extremely disappointed at the decision to terminate the current tanker competition," said Brandon Belote, a spokesman for Northrop Grumman.

A Northrop win would provide it the first manufacturing facility in North America. Los Angeles-based Northrop planned to build the tanker, which uses an Airbus A330 airframe, in Mobile, Alaska.

The US Air Force has been desperate to replace its current fleet of Stratotankers, which are pushing 50 years in age and becoming expensive to maintain and dangerous to fly.