A goopy residue of toxic mustard agent could delay the cleanup of the chemical weapon stockpile at Aberdeen Proving Ground (search), the General Accounting Office told the House Armed Services Committee on Thursday.

Ray Decker, director of the GAO's Defense Capability and Management section, said cleaning the toxic "heal" from the containers is the second part of a two-step process that has to be done before the cleanup is considered complete. He said it is questionable if the Army can finish both steps at Aberdeen by its December 2004 deadline.

"Things would have to go better than right," he said.

But Jeff Lindblad, an Aberdeen spokesman, said cleaning out the containers has been part of the plan for disposal of the mustard gas agent (search) since the beginning — though it is less vital than getting rid of the mustard agent itself that is in those 1,817 containers.

Lindblad said Aberdeen is ramping up on-site facilities to do the work, but he is not sure when it will start or when it will be complete.

Robotic equipment will eventually cut the containers in half and scrape out the toxic sludge, which will be sent offsite for processing, he said.

Each of the containers at Aberdeen holds about 170 gallons of mustard agent, the liquid form of mustard gas, a deadly blistering agent first used in World War I (search). Under the cleanup plan, the agent is pumped from the containers, neutralized with water and other chemicals and shipped to a DuPont Corp. (search) treatment center in New Jersey for disposal.

The process leaves a molasses-like coating called a "heal" on the containers, which remain at Aberdeen.

Container cleanup may have been in Aberdeen's original plan, but the amount of residual mustard agent left over in the containers was a surprise, Decker said.

So far, things have not gone "better than right" at Aberdeen. Only 152 of the containers of the mustard agent have been emptied; none have been destroyed.

The Department of Defense originally planned to have the chemical stockpile at Aberdeen destroyed by 2008. But after the terrorist attacks on Sept. 11, 2001, the Defense Department moved the destruction deadline to 2003, because the stockpile is a security risk.

The deadline had to be pushed back after a series of equipment failures, said Lindblad. And the base did not destroy any of the toxic liquid for six months during 2003 because of technical failings.

The stockpile is still a security risk, not only for terrorism, but also in case of earthquakes, tornados and lightning.

"We're still fighting a terrorist war. Time is of the essence," Lindblad said. "There always has been a risk."

Because of that risk, he said the key is to destroy the chemical agent first, not the containers.

Asked if Aberdeen would make the 2004 deadline, Lindblad said he did not want to make a prediction.

"We are encouraged. But this is a pilot facility. It's a one of a kind and we are going to encounter challenges along the way," he said.

CNS contributed to this report.