Jim McNerney, the chief executive of Boeing, said this week that a bruising transatlantic battle with Airbus over a $35 billion Pentagon contract risked damaging his company's relationship with the Federal Government.

Airbus and its partner Northrop Grumman were awarded the contract to supply air-refuelling tankers earlier this year, but after Boeing complained about the selection process, the deal has been scrapped and the tenders must be resubmitted.

Boeing's decision to protest the contract, which is likely to become the largest ever Pentagon procurement project, is understood to have angered the United States Air Force (USAF).

The USAF has repeatedly said that it believes the Airbus aircraft is the best suited to its needs and the recompetition will postpone a decision on the already much-delayed tanker contract by at least six months.

Part of the USAF's current fleet of tankers is 50 years old and replacing them has become the service's highest priority. Service personnel have privately expressed anger that Boeing has questioned their judgement in selecting the Airbus plane and delayed the tanker still further.

Mr McNerney, who was attending the Farnborough Air Show, said: "I realise that we took some risk with our relationship when we protested. We were very uncomfortable with that. We are very sensitive to our relationship with our customer and only after a lot of thought did we protest. We did take a risk." He added that it was the first contract protest initiated by the company in the past decade compared with 28 from its rivals.

Meanwhile, the chief executive of Northrop Grumman told The Times that he hoped Gordon Brown would intervene directly with the White House to press the case for the Airbus aircraft.

The wings for the Airbus tanker will be made at Broughton in North Wales and the Pentagon contract will help sustain 11,000 jobs there. Downing Street said last week that the prime minister would do whatever he could to help.

Ronald Sugar, the head of Northrop, said: "Certainly I hope Mr Brown and others in the UK back us. If they believe in transatlantic co-operation they should use their voice."

Loius Gallois, the head of EADS, which owns Airbus, said: "We are confident that having won this contract once we can win it again as ours is still the best aircraft."

Mr Gallois also said that the sale of the Filton factory near Bristol was progressing despite hurdles in negotiations with the proposed buyer, GKN. EADS has started talking to other possible bidders but the GKN offer, which is dependent on securing future supply contracts for Airbus aircraft, should prevail "in the next few weeks", Mr Gallois said.

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