Britain could drop its opposition to an "open skies" deal liberalising transatlantic air travel if there is a binding follow-on deal giving access to US domestic routes and airline ownership, an industry said.

The biggest air travel agreement in decades goes to EU transport ministers for approval this week and Britain, isolated in the 27-nation bloc in its opposition, is searching for an acceptable compromise.

"The likelihood is that the British go along," said the source last week in comments echoed by diplomats in Brussels. Britain is loathe to grant wider access to London's Heathrow airport without Washington easing its opposition to allowing European airlines to buy control of US carriers or fly on domestic US routes.

So far, the US Congress has provided stiff opposition to any compromise on the US routes or ownership issues.

London is especially keen to gain these concessions as the initial deal will expose British Airways and Virgin Atlantic to greater competition at Heathrow.

For decades, the lucrative Heathrow flights to and from the United States have been limited to just four airlines, two British and two American.

The industry source said the UK was looking at asking EU transport ministers to insist the United States agree to begin discussions on a follow-on pact within 60 days. "They are pursuing that as one option," the source said. That is eight months sooner than a January date for opening talks on a second-phase deal that EU Transport Commissioner Jacques Barrot referred to in the European Parliament. An EU diplomat said if Britain did win backing for the 60-day target date, it might try to use a refusal by Washington to go along with this as a reason to delay its own ratification and implementation of the "open skies" agreement. The British are also keen to have an automatic termination clause added to the "open skies" deal which would trigger a scrapping of the pact if a follow-on deal is not signed within 30 months, the industry source said.