Sources from both sides said an agreement giving more airlines access to Heathrow and US airports was likely to be signed in Washington late this afternoon.
"Baring any hitches I think that something may be announced,'' said a spokesman for the British side.
"I think everyone involved in the talks are hopeful that some sort of deal can be reached."
Any deal will involve allowing a second US carrier, United Airlines, to fly the Chicago-Heath-row route in competition with American Airlines.
Other airlines may be given greater access to UK regional airports.
Agreement would also likely see BA's temporary access to Philadelphia made permanent, and may even include arrangements for the airline to extend its code-sharing deal with USAir.
The Philadelphia route enables BA to improve the connecting flight arrangements it has with USAir.
The US side has also given strong indications that it plans to drop its "fly America" policy, in which US public officials are not allowed to use foreign carriers.
A sticking point during the current talks had been the size of aircraft United Airlines should be allowed to use on the Heathrow-Chicago route. Critics had said United should be limited to aircraft no larger than a 200-seat Boeing 747.
The current round of talks is the third since 1993, when US negotiators walked out. The negotiations have been protracted largely because of divisions among US airlines over the terms of an agreement.
A mini deal is seen as a way to break the impasse and a stepping stone to a more wide-ranging "open skies" air accord aimed at ending all restrictions on bilateral transatlantic services.
The next round of talks would be widened to include fares, cargo services, charter flights, further code-sharing, access to more airports and greater access to Heathrow.
American Airlines has been one of the fiercest critics of a mini deal, arguing that a piecemeal agreement that favours one or two airlines is wrong.
A spokeswoman said: "Mini-deals tend to benefit British airlines. We are in favour of complete renegotiation towards a total open skies policy."Reuse content