Mayor Marion Barry, under criticism for proposing once-a-week trash collection in only one part of the city, has decided instead to try reducing collection in six of the city's eight wards -- everywhere but the inner city -- beginning early next year.

Herbert L. Tucker, director of the D.C. Department of Environmental Services, announced the change in plans yesterday at a City Council committee meeting attended by more than 100 trash collectors fearful of losing their jobs if trash collections are reduced.

As a way to help balance his budget for the fiscal year beginning next Oct.

1, Barry had proposed last week a once-a-week collecton experiment using 82-gallon cans in Wards 7 and 8 and parts of Ward 6 -- all neighborhoods east of the Anacostia River.

City Council members, community representatives and union leaders objected.

The area, which already feels neglected by many city services, contains some of the poorest sections of Washington and also has some of the worst rat infestaton in the District, they said.

Yesterday, Tucker told the City Council's Transportation and Environmental Affairs Committe that public pressure led to modification of the plan. "The interest of the council, the interest of the citizens and the interest of the media" brought about the change, Tucker said.

Even with the modification, however, the proposal appeared headed for tough going before the environmental affairs committe, which must in the next two months make recommendation to the full council on funds for Barry's plan.

Council member Jerry A. Moore Jr. (R-At Large), chairman of this committe, said after Tucker's testimony, "I'm not going to cancel the concept of the program. . . But it can't work in the form it is presently set forth because the citizens don't want it. . . it has run into a psychological barrier that makes it pretty much impossible (to approve)."

Under yesterday's proposal, the system would be tried on one or two routes in wards 3,4, 5, 6, 7 and 8. There are about 600 homes on each route, according to Tucker aide Ann Witt.

Each residence on the route would be provided with a large, green, rolling trash can free of charge. (The cans cost the city $36 each.) For the first two months, trash still would be collected twice weekly.

Later, a once-a-week collection would be tried, Witt said. Some time before next October, the city would decide in which wards the program would finally go into effect, she said.

Witt, who briefed the council committe while one of the large, heavy plastic cans sat on display in the well of the council dais, was not able to say how much the expanded experimental program would cost. The cost of containers alone would be at least $129,600, she said.

Despite the announcement of the new proposal, City Administrator Elijah B. Rogers refused to say whether the east-of-the-river plan had been ruled out.

At the appropriate time, the mayor will make his announcement," was the only answer Rogers would give to repeated questions about the fate of the original proposal.

Moore was not the only council member to express opposition. Council member Wilhelmina J. Rolack (D-Ward 8) said she was "unalterably opposed" to the program because it would eliminate jobs and increase rat problems in Anacostia.

Other council members complained that the big trash cans could be a safety hazard for children who might play with them on the streets. "These probably will (become known as) the trash cans that took over the streets of Washington, D.C.," said council member John Ray (D-At Large).

Council member Hilda Mason said she feared that children might climb inside the cans. "I would never vote for that," she said.

The east-of-the-river proposal would save the city about $700,000 and eliminate 38 jobs. The city also proposes to contract with a private firm to collect trash in Wards 1 and 2, where most trash is already hauled by private firms. In all, 132 positions in the trash collection division would be eliminated next year, Tucker said.