At a Washington press conference given by the chairmen of American, United and Delta airlines, the Bush administration was warned that the BA-USAir agreement would cost jobs, stifle competition and threaten the structure of the US airline industry.
The fiercest criticism came from Robert Crandall, of American, who warned that if the US did not secure 'total' liberalisation of air services between the two countries it would be left 'on a one-way street to second-class status'.
Stephen Wolf, of United, described the deal as illegal under US law and said that, if approved without concessions, it would be 'the worst mistake our government has ever made in international aviation'.
Mr Crandall said that total liberalisation would mean giving US airlines substantially increased access to Heathrow and unlimited rights to serve any destination within and beyond the UK.
Previously, United and American had indicated that they would back the BA-USAir deal if they were allowed to fly to more UK regional airports in return. A BA spokesman said: 'They are trying the filibustering approach.'
Richard Branson said he expected a decision on a link-up between Virgin Atlantic and Dan-Air this weekend. .
Air France is cutting a further 1,500 jobs after reporting an increase in first-half losses from Fr1.16bn to Fr1.5bn ( pounds 181m).