WASHINGTON — The Defense Department has warned state environmental officials around the country not to take enforcement actions against toxic waste sites on military bases — or the Pentagon will not pay for cleanup as required by federal law.

The military's resistance to environmental enforcement is slowing efforts to clean some potentially dangerous sites, advocates for state agencies say, and forcing the New York state Department of Environmental Conservation to be more delicate than usual as it negotiates cleanups of several areas at Fort Drum.

At issue are the agreements between most states and the Defense Department that outline policies for cleaning contaminated sites. Although those agreements have been in place for years, the Pentagon in 2006 announced a new approach to some of the fine print, including how the federal government reimburses states for the costs of remediation and removal of toxic substances.

The biggest change, from the states' perspective, was the announcement that any enforcement action by a state — including a single notice of violation — would lead the department to withhold reimbursements if state officials acted without entering a lengthy arbitration procedure first.

The department also announced that it would not pay for work such as training and policy development if it is not directly related to a specific site. So a state agency could not be reimbursed for sending an environmental staff member to a seminar on cleanup of defense sites generally, for instance, even if that is his or her sole responsibility.

The military's standoff with state environmental agencies comes as it is also fighting the U.S. Environmental Protection Agency's enforcement at federal Superfund toxic sites.

"We think this is related," said R. Steven Brown, executive director of the Environmental Council of the States, representing state environmental commissioners.

At Fort Drum, the state DEC and the Defense Department are negotiating two consent agreements that will lead to cleanup of hazardous sites. DEC also recently applied to the U.S. Army Corps of Engineers for a two-year extension of its contract on cleanup policies at military sites throughout the state, called a Defense State Memorandum of Agreement. The most recent agreement expired at the end of June.

Cleanup at Fort Drum already is under way on a "voluntary basis," DEC reported, including remediation of leaking or spilled fuel at Wheeler-Sack Army Airfield and at the former Gasoline Alley on the older section of the base.

Other sites are polluted from explosives or from leaching pesticides and heavy metals, such as from an old landfill. At Gasoline Alley, cleanup includes the planting of thousands of willow trees to gradually filter and disperse contamination.

None of the sites poses an immediate risk to the public outside Fort Drum, DEC reported.

But cleaning at parts of Gasoline Alley and the old landfill, for instance, await consent agreements, according to DEC and the EPA. One of those agreements, negotiated for about two years, is undergoing final review by lawyers, said Kent Johnson, the DEC engineer managing some of the Fort Drum sites.

Consent orders from DEC typically outline enforcement actions such as fines if a polluter fails to comply with the terms, a spokeswoman said, although Mr. Johnson said he was not aware of any reference to fines in the agreement with Fort Drum.

"There's always been a very good working relationship" with Fort Drum, Mr. Johnson said.

But state environmental commissioners say the Pentagon's approach takes the teeth out of environmental laws.

"This linkage of DSMOA funding to state enforcement amounts to economic coercion, undermines basic state authorities and has many states considering returning to expensive cost recovery actions," wrote Carolyn Hanson, a senior project manager with the Environmental Council of the States, in the organization's "Green Report" newsletter.

Pentagon officials say their policy has not changed. In a series of letters to state officials and the Environmental Council, defense officials maintained that the agreements have always required dispute resolution before enforcement. The department's deputy undersecretary for installations and environment, Philip W. Grone, answered the complaints in a letter to the ECOS last November, before leaving the department.

"This position is not a change in interpretation," Mr. Grone wrote. "States have always followed accordingly."

But state officials say the Defense Department has no right to dictate a state's enforcement authority. Enforcement is separate from the cleanup agreements states sign with the military, Mr. Brown said.

Unhappy with the Pentagon's response, the council hoped retirements of some key Pentagon officials would bring a new approach this year, Mr. Brown said.

"There was a little glimmer of hope," he said, including a meeting with defense officials in February. But nothing changed.

Mr. Brown's organization has contacted congressional offices, seeking legislation to stop the Defense Department from tying cost reimbursements to environmental enforcement and to allow a broader interpretation of which costs may be reimbursed. At a minimum, he said, the group wants congressional hearings, although he noted time is running short before Congress takes its summer recess.

In the Senate, the issue would face the Environment and Public Works Committee, on which Sen. Hillary Rodham Clinton, D-N.Y., serves. She also is a member of the Senate Armed Services Committee.