In a joint letter sent Thursday to assistant Army Secretary Claude Bolton, they called on the Army to instead pursue its original disposal plan for the nerve agent residue.

That plan called for disposing of the waste on-site at the Newport Chemical Depot using a high-pressure treatment that would yield a solid that could then be buried in a landfill.

If the Army moves ahead with its plans to ship the waste to a DuPont plant in Deepwater, N.J., the activists said it was certain to result in lawsuits, delays, additional technical and safety questions and heightened opposition.

"It is time for the Army to quit fooling around and seriously assess its options for treatment of the hydrolysate in an open, transparent manner," their letter stated.Nancy Ray, a spokeswoman at the Army's headquarters, said Bolton was traveling Thursday and had not yet seen the letter and therefore could not comment on its proposals.

In May, an Army contractor began destroying more than 250,000 gallons of VX, a Cold War-era chemical weapon, using a chemical neutralization process at the Newport depot, about 30 miles north of Terre Haute, Ind.

The project was halted in June after a leak but resumed last week on a limited scale amid ongoing testing. Army officials estimate the project will take about 30 months and produce up to 4 million gallons of a caustic wastewater called hydrolysate that the Army wants to truck to DuPont for treatment and eventual discharge into the Delaware River.Environmentalists and state officials in New Jersey and Delaware oppose that plan, saying it could damage the river and pose a threat to residents if an accident occurs during shipping.

Acting New Jersey Gov. Richard J. Codey has vowed that the state would use every means possible to prevent federal officials from using the New Jersey Turnpike to haul in the residue.Sara Morgan, a spokeswoman for Citizens Against Incineration, said the Newport group, which led protests that prompted the military to drop an earlier plan to incinerate the VX waste, wants it to be treated on-site.

"We would not want someone shipping waste of this nature to our state and we don't want to be doing that to some other state," she said.

Craig Williams, director of the Chemical Weapons Working Group in Berea, Ky., said that despite growing opposition to its plan -- and the failure of a previous proposal to dispose of the hydrolysate at a plant in Ohio -- the Army appears set on pursuing the DuPont disposal.

"It has been `Carry out the order, Sir,' ever since, regardless of the serious issues and challenges associated with this approach," Williams said.

Williams and the other groups that signed the letter to Bolton want the Army to build a high-pressure waste treatment facility at Newport. After the hydrolysate there is treated, they want the Army to move the equipment to the Blue Grass Army Depot in Richmond, Ky., to treat waste there after its own VX stockpile is destroyed.

He said the Army has exaggerated technical problems involving the high-pressure treatment process, called supercritical water oxidation.Jeff Lindblad, a spokesman for the Army's Chemical Materials Agency at Aberdeen Proving Grounds, said the Army adopted its plan to ship the hydrolysate off-site in mid-2001 after tests conducted in Texas using the high-pressure process ran into serious technical problems.

He said that process could still work but said the military has estimated that pursuing it would add another two years -- and add $300 million in costs -- to the project to destroy Newport's VX and dispose of the hydrolysate.

Tracy Carluccio, director of special projects at the Delaware Riverkeeper Network, said her group would sue to stop the Army's off-site shipment plan to New Jersey, if needed.

Aside from growing opposition among government officials and activists, the Army's off-site treatment plan faces scrutiny from the U.S. Centers for Disease Control and Prevention.

Sharon Finlayson of the New Jersey Environmental Federation said she believes the Army will ultimately fail to win approval for its off-site shipment plan.

"We believe the Army has wasted a lot of precious time trying to peddle this treatment plan from one state to another, trying to get rid of it," she said.