BALTIMORE, DEC. 14 -- Eating oysters today in symbolic support of the Chesapeake Bay, the governors of Maryland and Virginia hailed an agreement to clean up the country's largest estuary as they prepared to sign the document here Tuesday.

"It is difficult to overstate the importance of this new pact," said Virginia Gov. Gerald L. Baliles. Maryland Gov. William Donald Schaefer said the agreement "sets tough timetables, makes us all work at top speed . . . . We believe in this."

The 12-page agreement grew out of a simple, one-page statement in 1983 by the governors of Maryland and Virginia and the mayor of the District to try to clean up the bay. The new pact commits Maryland, Virginia, Pennsylvania, the District and the federal government to a series of goals and timetables aimed at restoring the health of the pollution-plagued bay.

But the governors, at a news conference today, declined to discuss the plan's specific price tag, and they scoffed at criticism by environmentalists that the agreement is not specific enough and sidesteps the tough issue of toxic pollution from industrial plants.

Baliles said many citizen comments and suggestions were incorporated into the final draft. "The process created in 1983 is working. The proof is here. This is an agreement to act."

The Virginia governor said he had learned that "some groups will never be satisfied. I don't think the criticisms are accurate. The agreement has specifics."

David Carroll, Schaefer's bay coordinator, said the final agreement contains stronger and more specific language than an August draft. It specifically calls for management plans to improve the yield of oysters, shad and blue crab. He said the agreement also puts governors, rather than lower-level officials, in charge of an interstate committee that will implement the agreement.

The agreement also commits the parties to come up with a plan to alleviate toxic pollution and to take action within a year, noted Lee Thomas, administrator of the U.S. Environmental Protection Agency, who attended the news conference.

"You can't get ahead of your scientific knowledge," Thomas said, alluding to the current information available on safe levels of toxic pollution.

Ann Powers, general counsel of the Chesapeake Bay Foundation, a private organization that had been critical of the draft agreement, said today that the pact was "a far cry better than the 1983 agreement. It takes us a big step further." Environmentalists were especially pleased by the commitment to reduce the amount of nutrients in the bay by 40 percent by the year 2000. These chemicals, such as phosphorous and nitrogen, consume oxygen in water, choking the underwater grasses that nurture and support aquatic life.

The governors said they will submit bay proposals to their respective state legislatures in January, with price tags affixed.

"Well-crafted words and high-blown rhetoric will not save the bay," Baliles said. "We've got to take this agreement to our legislatures and sell it, and, given what we are attempting, that will be no snap."

While declining to estimate the future cost of bay cleanup, Baliles said that since 1983, the federal and state governments have spent $250 million toward that end.