WASHINGTON (AP) _ Backers of a House-passed bill that calls for a smoking ban on most domestic airline flights are encouraged by an endorsement of their goals by the chairman of a key Senate subcommittee.

Dozens of members of health and consumer organizations lobbied senators Wednesday on behalf of legislation that would prohibit smoking on airline flights of two hours or less, which represent about 80 percent of all domestic trips.

Before they visited lawmakers' offices, the supporters received from Sen. Frank Lautenberg, D-N.J., chairman of the Senate transportation appropriations subcommittee, his written agreement with their goals, alhthough he left open the question of whether he might offer somewhat different legislation.

Rep. Richard Durbin, D-Ill., author of the version passed July 13 by the House, conceded at a news conference that the struggle in the Senate would be difficult, but added, ''It's a battle that can be won.''

Lautenberg was not present at the news conference because of the death of his mother.

But in the written statement, he said, ''I intend to do everything I can to include a strong provision ... to protect the health of non-smokers and flight attendants.''

Lautenberg in the past has coupled his support for the effort with qualms about the mechanism the House bill uses. It would block federal aid to airports that service flights of two hours or less that allow smoking.

The House language was part of the 1988 transportation appropriations bill. Lautenberg's subcommittee hopes to begin considering its version of the legislation later this month, and Lautenberg indicated he would work for some type of airline smoking restrictions.

''The ball is in my court and I intend to do what is necessary to protect the health of the flying public and the people who work on the airplanes,'' the senator's statement said.

Jim Abbott, Lautenberg's press secretary, said the senator was considering several options but declined to describe them.

Two lobbyists who work for groups opposed to the House bill - Walker Merryman of the Tobacco Institute and Robert Wigington of the Airport Operators Council International - said in interviews that they heard Lautenberg might work for a ban on smoking on all domestic flights.

Much to the surprise even of Durbin and his co-sponsor, Rep. C.W. Bill Young, R-Fla., the provision was approved by the House by a close 198-193 vote. Passage could be even more difficult in the Senate, where tobacco-state lawmakers threaten a filibuster, which stalls legislation by limitless debate.

''If they want an appropriations bill, this won't go on it, because if it is they'll never get the bill,'' Mark Fleming, an aide to Sen. Jesse Helms, R- N.C., said in an interview. ''We have a system over here called the filibuster.''

The news conference was attended by dozens of members of health groups such as the American Cancer Society and the American Diabetes Association, which support the smoking ban and whose representatives spent Wednesday lobbying senators.

Also present was actor David Birney, who said, ''Anything we can do to make the environment a little safer in the air, we should do.''