BA's chief executive, Bob Ayling, told a conference in London that any attempt by regulators to confiscate slots would be "wrong, irrational, unfair, potentially corrupt and against the public interest".
The comments are likely to bring BA into conflict with competition authorities on both sides of the Atlantic as speculation mounts that the Office of Fair Trading is poised to recommend that the deal be referred to the Monopolies and Mergers Commission.
Rival US carriers have mounted an unprecedented attack on the BA-American deal, which will give the combined group 60 per cent of UK-US flights, on the grounds that the two airlines would gain a monopoly on several routes from Heathrow to US cities.
Some of the rival airlines, including TWA, have said they will drop this opposition if BA gives up some of its much-coveted slots at the airport, the world's busiest. Mr Ayling told delegates the best way to reallocate scarce slots was to buy and sell them in the marketplace.
"There will be a massive and natural development in the market for used slots traded between airlines at prices governed by the laws of supply and demand," he explained. However US carriers have argued this would simply allow BA to earn even greater profits should it decide to divest itself of some of its slots after all.
His comments came after a senior US Government official strongly attacked the UK authorities' stance over the troubled open skies talks, aimed at liberalising UK-US air travel. Mark Gerchick, a deputy assistant secretary at the US department of transportation, accused British officials of "endless, narrow, tit-for-tat bargaining" over every stage of talks.
On Tuesday the US called off the latest round of talks, due to be held in Washington, claiming the British blueprint for a deal was "way off the open skies mark". The US has said it will only grant the BA-American alliance regulatory approval if it can secure an open skies agreement with the UK.