The chairman of a special Maryland transportation committee said yesterday that the Department of Transportation will recommend a 5 percent sales tax on the price of gasoline to finance the state's faltering road and mass transit program.

However, the proposal could run into immediate opposition from legislators on the transportation panel, which is scheduled to decide on a plan tomorrow that can be recommended to Gov. William Donald Schaefer.

Late last week, House Speaker R. Clayton Mitchell Jr. (D-Kent) reiterated his opposition to any increase in gasoline taxes, telling one interviewer that he believes lagging revenue will rebound if gasoline prices decline. Mitchell has been the principal opponent of a gas tax increase as the General Assembly prepares to open its 1991 session on Wednesday.

William K. Hellmann, chairman of the Transportation Revenue Committee, said in an interview yesterday that the panel's members had spoken in favorable terms about applying the state's 5 percent sales tax to gasoline, but had already rejected a proposal to increase the current gas tax of 18.5 cents per gallon by 3 cents.

The sales tax proposal would raise an estimated $540 million for state transportation projects, the equivalent of increasing the per gallon tax by 7.5 cents. The benefit of the sales tax, Hellmann said, is that tax revenue would increase along with gasoline prices. As prices have risen since Iraq's Aug. 2 invasion of Kuwait, gasoline usage in Maryland -- and consequently tax revenue -- has fallen.

State transportation officials projected recently that the transportation trust fund will be more than $500 million short of the amount needed to finance the already approved road, bridge and mass transit program through 1996.

Transportation officials will recommend tomorrow that Hellmann's committee, which includes three senators and three House members, approve the sales tax on gasoline, as well as increases in fees charged by the Motor Vehicle Administration. Hellmann said the committee would consider a $1 billion revenue package that also would allow the state to issue $500 million in bonds.

Of the total, he said, $600 million would go to close the gap in the current program, which, among other things, would assure that money would be available to construct the proposed trolley line between Silver Spring and Bethesda. In addition, $400 million would go to preserve the current road system, $130 million for operating initiatives and $370 million for new roads, bridges and for improvements at Baltimore-Washington International Airport.

Schaefer has not said whether he supports higher gasoline fees. Yesterday, an aide said the governor would wait to see what the Hellmann committee recommends.

However, one House member who asked not to be identified said last week that House members on the committee may not support any increase this year.

Hellmann, a former secretary of transportation, declined to predict what the panel will do. "I think the committee will end up with a consensus on most of the recommendations," Hellmann said, adding that he expects the committee to alter the proposal presented by the Department of Transportation.

Last month the Department of Transportation suspended new construction projects until it studies the costs and whether funding will be available to complete them. Among the projects delayed by that decision was the widening of Route 50 between the Patuxent River and Annapolis, a heavily traveled route for beach-bound traffic.