The Metro board, deadlocked over what to charge for rush-hour train rides, postponed a final decision yesterday on a proposed fare increase.

A consensus seemed to have formed to raise rail base fares and most bus base fares from 65 to 75 cents, but members could not agree on mileage fees, which are tacked onto base rail fares after three miles of rush-hour travel.

There was also disagreement over whether to impose a new 5-cent charge for bus-to-bus transfers and over proposed increases in special fares for elderly and handicapped persons.

The board's failure to act yesterday could delay implementation of the fare increase, originally set for April 2. Staff members had said a decision was needed by yesterday to provide enough time to reprogram fare gates for the new fares by April 2.

The debate over mileage fees, heard in a committee meeting before the full board convened, split member jurisdictions along long-established lines over whether short-haul riders should subsidize their long-distance counterparts or vice versa. "Who pays is the issue," said D.C. member Thomas Downs.

Representatives from D.C. and Virginia, where residents tend to take short rail trips and therefore feel less effect from higher mileage fees, spoke for raising those fees from 13 to 15 cents a mile.

Maryland commuters, by contrast, take some of the 39-mile system's longest routes, riding downtown from New Carrollton, Addison Road and Silver Spring. They are hard hit by mileage rates, and that state's representatives accordingly try to keep those rates low.

Over Maryland's opposition, the committee finally recommended a 75-cent base rail fare and 14-cent mileage fee, with jurisdictions making up in extra subsidies what their own riders would have paid if the mileage rate were 15 cents. Maryland would have to pay about two-thirds of the $800,000 shortfall, according to state officials.

The board will meet again next Thursday to make a final decision.

Debate yesterday was complicated further by disputes among D.C. representatives over proposals to raise fares for elderly and handicapped riders. Jerry A. Moore and Hilda Mason, appointed by the City Council, opposed those proposals.

Downs and Gladys W. Mack, D.C. representatives appointed by Mayor Marion Barry, supported the proposals. Downs said an increase is justified since the special fares had not changed since 1975.

Mason said Barry had earlier proposed free fares for the elderly and handicapped. Mack responded that the D.C. economy "has changed dramatically in the past 12 months" and the city no longer has the money for such a program.

D.C. split along the same lines over the proposed bus transfer charge, with Moore and Mason opposing it, and Downs and Mack expressing reluctant support. Most bus transfers occur in the city.

Downs, raising another potential negotiating problem for the fare package, said that his support for the bus transfer charge, for which Maryland has actively lobbied, was tied to that state's acceptance of a 15-cent mileage fee.