Washington ? The Environmental Protection Agency took action Friday to curb the authority of its field agents to enforce rules protecting the nation’s wetlands, and it began a process that could cut wetlands protection even further.

Environmentalists quickly denounced the actions as an attack on the Clean Water Act, and they insisted the EPA’s moves had the potential to harm as much as 60 percent of the nation’s wetlands.

“This is just one salvo in the Bush administration’s all-out assault on fundamental protections for our air, water and public health,” said Gregory Wetstone, advocacy director for the Natural Resources Defense Council. “The Bush administration has intensified its effort to undermine our landmark environmental laws.”

EPA Administrator Christie Whitman insisted that the administration remained committed to a policy of “no net loss” of wetlands in the United States.

“We are committed to protecting America’s wetlands to the full extent under the Clean Water Act,” she said.

The areas involved — known as “isolated wetlands,” because they generally are not connected to other waterways — amount to no more than 20 percent of the nation’s total waterways and may be only half that, an EPA spokesman said, dismissing the environmentalists’ claims to the contrary.

By the agency’s own admission, however, the ability of EPA field agents to enforce the clean water law will be curtailed under the new rules, leaving state, tribal and local governments to decide the fate of many isolated wetlands.