WASHINGTON -- The Bush administration is considering a revision of the government's official definition of "wetlands" that environmentalists charge would eliminate protection for millions of acres of vulnerable wildlife habitat.

A draft of the new document, made available to The Associated Press by an administration official on Tuesday, says the previous definition "grossly exaggerated" the country's real wetlands, mostly by not requiring that they be very wet.

The definition, contained in an interagency wetlands manual that took effect in March 1990, upset landowners and developers who found that they needed government permits to build on land they did not consider wet.

"Some owners of apparently arid land have been confused if not outraged," EPA Administrator William Reilly said when asked about the new draft.

Reilly said the uproar "created an untenable problem" for administering a program intended to protect precious swamps, bogs and marshes that are vital for flood control and wildfowl habitat.

Reilly said the EPA's draft for a new manual was sent to the White House on May 6 for review by the Office of Management and Budget. The review is expected to take a few weeks.

One of the key changes involves the question: How wet is a wetland?

The current definition says water must come within 18 inches of the surface for at least seven days of the growing season.

The draft would be stricter, requiring that land be inundated or saturated all the way to the surface for at least 14 consecutive days in the growing season.

The Izaak Walton League, a conservation group, objected to the change. Linda Winter, the group's director of wetlands programs, said a scientifically sound definition for a wetland "is being thrown out and ignored for political reasons."

The result is likely to be that "whole groups of wetlands will be deleted," she said. "We need to say enough is enough. We can't afford to lose any more of these wetlands."

Reilly said he could not confirm estimates that 4 million to 10 million acres would no longer be considered wetlands under the new definition.

"I don't think anyone involved in the program could make an estimate," he said. "We did not intend to add or subtract from the genuine wetlands of the United States."

The Fish and Wildlife Service has estimated that about half of the original wetlands in the continental United States have been destroyed in the past 200 years.

Swamps, marshes and bogs used to be considered wasteland, and the government encouraged draining them for farming or development.

However, under the 1974 Clean Water Act, the owner of land classified as wetland needs a permit from the federal government to build on it. The law generated little controversy until the 1990 manual was issued, covering much property that people had not considered wetlands before.

"It's just a program that's out of control," said Bernard Goode, former official of the U.S. Army Corps of Engineers who helped draft the 1990 definition.

"Had I known then what I know now, I would have insisted that there be more surface water for there to be a wetland," Goode said. "Areas that no one in their right mind would call a swamp, a bog, a marsh, are being called federal wetlands."