Will Overnite truck drivers pass the ammo? Will Texaco gas the tanks? Humana staff the first-aid station? And will Ridgewell's cater the battle?

Improbable as those may sound, that's what a large military reserve organization said yesterday that the Clinton administration is considering.

In what one former Clinton appointee describes as a decision with far-reaching implications for military strategists, the Office of Management and Budget will publish new guidelines today for what military jobs civilian contractors can handle. Under those new rules as many as 400,000 military jobs, many of them battlefield support positions typically filled by reservists, could be given to contractors, said Jayson L. Spiegel, executive director of the Reserve Officers Association.

Pentagon officials disputed what Spiegel, a former deputy assistant Army secretary, called "a dramatic expansion" in military jobs being offered to contractors.

Spiegel, who until recently wrestled with such manpower issues in the Pentagon, said the Joint Chiefs of Staff had opposed the OMB language. They want to keep all combat support jobs filled by uniformed personnel who would be subject to military rules and discipline.

Spiegel and other reserve advocates say they will argue that there is no certainty that contractors will show up for work under hostile fire. "Contractors are going to be killed" if the plan is enacted, he said, citing an Army estimate that upward of 576 contractors could be killed if deployed in combat operations.

A Pentagon official familiar with the issues said Spiegel's estimate was far too high. "He's so far off base I don't know where he's coming from," said the official, who asked not to be named.

The official said that no more than 50,000 military jobs could be at risk under the new OMB rules. The services previously announced plans to study contracting out upward of 229,000 positions, but it is not yet clear how many of those will be uniformed positions and how many are civilian positions, the official said.

The new OMB rules declare that "activities performed exclusively by military personnel who are subject to deployment in a combat, combat support or combat service support role" are among the jobs considered to be inherently "governmental." That language seemingly would make them less vulnerable to contracting.

But Spiegel said that because many combat support jobs, such as those of truck drivers, doctors and cooks, are also performed by civilians, "the final OMB rule will still provide for contracting out of significant portions of battlefield logistics systems."

Military contractors have accompanied troops into battle for decades, but until the Gulf War they were mostly specialists for particular weapons systems.

To implement the plan, the Pentagon must first identify and publish a list of the jobs it wishes to offer contractors. It then must accept bids on them and find other work for the military personnel the contractors would replace. That process could take months, if not years. Any large-scale contracting is almost certain to attract congressional hearings, officials said.

If the new OMB rules result in reductions in reserve forces, that is certain to be resisted by the politically powerful groups, including Spiegel's organization, that represent reserve and National Guard forces in Washington. Any effort to contract out specific jobs is also subject to administrative appeals and other delays.

Republicans in Congress have argued that the military has been slow to contract out work that could be easily and economically performed by the private contractors.

Last year they pressed Congress to enact legislation that requires all government agencies to list for possible contracting all jobs that are "not inherently governmental." It was that legislation, the Federal Activities Inventory Reform Act of 1998, that prompted the OMB language.

No part of the military would be hit harder than the Army and its reserve forces, which under recent restructuring now contain many battlefield support positions previously placed in the active-duty force. Under an analysis Spiegel's Army office performed last year, nearly 228,000 uniformed positions in the Army will have to be considered for contracting under the OMB ruling.

Spiegel said some members of the administration, including Deputy Secretary of Defense Jacques Gansler, have supported much more contracting than the service chiefs have endorsed. "The Army's problem is that we have too many soldiers on the battlefield," Spiegel quoted one Gansler aide as telling him. "We need two types of people on the battlefield, contractors and trigger-pullers," Spiegel said the aide told him.

Gen. Henry H. Shelton, chairman of the Joint Chiefs of Staff, argued against including military personnel in the contracting review. "We must conduct risk assessments to understand impact on warfighting capability, operational tempo and readiness before competing certain positions," he said.