Arms control experts say the plan could run afoul of the international Chemical Weapons Convention, to which the United States is a party.
The plan calls for demonstrating the feasibility of a "safe, reliable" chemical immobilizing agent or agents for nonlethal applications in appropriate military missions and law enforcement situations, according to the document, Chemical Immobilizing Agents for Non-lethal Applications, a solicitation for corporate bids to perform the research.
If proven effective and safe, such "incapacitating" agents might be used for a wide range of missions, including peacekeeping, embassy protection, and counterterrorism.
The agents might also be used for common law enforcement purposes ranging from "hostage and barricade situations" to close proximity encounters such as "bar fights and stopped motorists," the document says.
A first phase of the program for initial research was contracted for in 2000 and has been completed. The military has not commented on when or if the second of three planned phases might begin.
The program is a concern to some arms control experts, who say it could lead to violations of the Chemical Weapons Convention and more generally undermine the treaty and other international norms.
"I do see as very destabilizing the development of new nonlethal weapons, whether they're riot control agents or not, being done by the military, for military purposes," Mark Wheelis, a microbiologist at the University of California at Davis.
It could "seriously erode the norm against military use of chemicals as weapons," he said.
Russian authorities used such an agent last month to incapacitate Chechen hostage-takers and rescue more than 600 hostages. While knocking out the Chechens, the fentanyl-based agent also killed 118 hostages, authorities said.
Without success so far, the U.S. military and Justice Department for years have sought to develop chemical incapacitants considered sufficiently potent and safe.
During the 1960s, the U.S. military put a substantial amount of money into developing a delirium-causing agent called BZ. By the mid-1960s, the Army had stockpiled and stored in military depots cluster munitions for delivering BZ.
Those munitions were dismantled and the BZ destroyed according to U.S. government declarations and, according to a 1997 Army history, there were at that time no temporarily incapacitating munitions in the arsenal. The history cited the inability to find an agent that would satisfy "practical and political concerns."
Then the military, through a program dating back to the 1970s called Advanced Riot Control Device, conducted research on variants derivative of fentanyl-sufentanil and carfentanil-but found they could cause a halt in respiration in humans. Subsequent research involved mixing or chasing it with an antidote naloxone to reduce the danger of respiratory failure.
The Army in May 2000 awarded a contract for the first phase of the plan described in the solicitation to the Michigan company Optimetrics.
Developing a safe chemical incapacitant is "a very, very difficult problem," said Parker Ferguson, the primary researcher on contract.
"I think the event in Russia is fairly indicative of the problems that one would face in trying to do that," he said.
Theodore Stanley, an anesthesiology expert at the University of Utah Medical School, said U.S. authorities have hesitated to develop chemical incapacitants in part because they can be controversial to use.
"Think about this: If you knew your government was conducting research and spending a significant amount of money so they could put something in the atmosphere and anesthetize an entire state or city in a minute, you might be upset with that," he said.
He said, though, that that risk could be outweighed by the benefits.
"If you could do that safely, and you saved that for very special cases, something like this [the Russian crisis], you had that capacity, you were trained and you could handle this, people would pat you on the back and say you saved the day," he said.
Ferguson declined to comment directly on the new research, citing a need to maintain confidentiality. The Pentagon's solicitation did provide some indication of the scope of the study and its goals.
If the technology is proven, potential military uses might include "meeting U.S. and NATO objectives in peacekeeping missions; crowd control; embassy protection; rescue missions; and counter-terrorism," it said.
Potential law enforcement uses by domestic agencies, the solicitation also said, include: hostage and barricade situations; crowd control; close proximity encounters such as, domestic disturbances, bar fights and stopped motorists; halting fleeing felons; and prison riots.
The research would analyze "recent breakthroughs in the pharmacological classes such as anesthetics/analgesics, tranquilizers, hypnotics and neuromuscular blockers."
"Recent pharmaceutical developments suggest that new approaches to safer chemical immobilizers with improved performance characteristics may be available," it said.
Arms control experts say regardless of how safe agents can be made, development and use of such agents by the military could run afoul of the international Chemical Weapons Convention, depending on their intended uses.
Fundamentally, the treaty prohibits using any chemical agents for warfare, while allowing for unspecified law enforcement use, and for riot control situations if the agent has only temporary side effects.
"The convention doesn't ban chemicals, it bans purposes under which those chemicals are applied," said Jean Pascal Zanders, project leader on chemical and biological warfare for the Stockholm International Peace Research Institute.
Experts see the administration's plan potentially in conflict with the treaty with respect to such military purposes such as peacekeeping, counterterrorism, search and rescue and crowd control.
Wheelis contends the U.S. military has not publicly made the case that using chemical incapacitants for such activities would be legal.
"Not only do you have to show that this is not a means of warfare, you also have to demonstrate that this is law enforcement," he said. "My view is the Pentagon has to demonstrate proactively that this is legal."
Using chemicals under such circumstances, he said, might be allowable if they were specifically authorized as law enforcement activity either by the country where they were used or by the U.N. Security Council.
Two of the potential uses that might pose problems with respect to the treaty are peacekeeping and counterterrorism, said professor Matthew Meselson, co-director of the Harvard Sussex Program on Chemical and Biological Warfare Armament and Arms Limitation noting the treaty expressly forbids chemical weapons use for warfare.
"You could imagine them in various flavors, some of which sound fine and some of which don't," he said.
"In peacekeeping, if it is against an organized armed unit, that definitely would be warfare," he said.
It is too soon to tell whether the program violates the treaty, Zanders said. He added, though, another part of the document could point to a potential treaty breach.
The document said the Pentagon's Joint Nonlethal Weapons Directorate found the technology falls under its broad core mission area of "incapacitating personnel" and could be used for "clearing of facilities" and "area denial."
"These are some of the core purposes of using chemicals in military warfare," he said.
There is little publicly available information explaining how the U.S. military views the constraints of the treaty on the use of chemical incapacitants. A slide show summarizing a Navy assessment presented in April 2001, however, suggested the Navy considers such agents allowable if incapacitation is temporary, for riot control in military operations other than war, and if it discriminates between civilians and combatants.
The slide show, presented by a Marine Corps attorney-advisor, suggested chemicals might also be used "defensively," such as against rioting prisoners, in situations where civilians are used as shields, for search and rescue, and for "rear areas security."
The Pentagon solicitation itself tacitly acknowledged use of the technologies could pose a challenge to the requirements of the convention.
The second phase of the program requires research to "determine implications of the Chemical Warfare Convention (CWC) for proposed scenarios of use" of the chosen material and "select optimum scenario(s) of use."