Mr Karel Van Miert, Competition Commissioner, wants BA and American to surrender 353 take-off and landing slots a week at Heathrow - equal to 25 round trips a day - and reduce services on some transatlantic routes as the price for approving the deal.
But Don Carty, president of American, said on a visit to London that it was only prepared to surrender about half that number, describing the Office of Fair Trading's recommendation that 168 slots be given up as acceptable. He also reiterated American's insistence that it would not give the slots away for free, pointing out that it had paid TWA $450m when it took over its services into Heathrow in the late 1980s.
Mr Carty also indicated that American expected the support of the US government in fighting its corner, saying that some of Mr Van Miert's proposals were totally inconsistent with US competition policy.
The US Under Secretary of State, Stuart Eizenstat, has said he would be concerned if the conditions imposed by Brussels were such that it stopped the alliance going ahead and prevented open skies across the Atlantic.
"In terms of giving away slots we have reached the limit," said Mr Carty, adding that the price Brussels was asking was not one that it would pay.
However, he said the two airlines would not, as earlier suggested, walk away from the alliance if they were still waiting for regulatory clearance in November when they attend the bi-annual slot conference in Melbourne.