Pentagon officials intend to set aside more than $13 billion to cover the upfront cost of base closures over the next several years, but that pot of money will be far short of the total price tag, forcing the services to raid their budget plans to pay for additional costs.

For the Army alone, that might amount to between $500 million and $1 billion annually over the next four or five years, a senior military official said Thursday, adding that officials do not yet know where the money will come from.

The $13 billion "wedge" Defense Secretary Donald Rumsfeld is expected to ration to the services is merely "down-payment money," the official said. "It doesn't cover all the costs in the first six years."

Pentagon leaders have said the tab for this base-closure round will come to $24 billion, including the costs of military construction projects and the relocation of military personnel and families. The consolidation of bases will ultimately generate $49 billion in savings, Michael Wynne, the Pentagon's acquisition secretary, told the commission in May.

Base closures "may have a 20-year payback, but you have to pay in the first year," the official said.

Rumsfeld released his BRAC recommendations in May, which include the closure of 33 major domestic military installations. The independent BRAC commission is evaluating the secretary's recommendations and will submit its own list to the White House Sept. 8.

On top of the shortfall in the Pentagon BRAC fund, the services must pay for environmental cleanup, which was not fully calculated in the department's base-closure cost analyses, the official said.

In previous base closures, environmental cleanup amounted to roughly 40 percent of total BRAC costs, though those figures differ widely per installation, depending on individual communities' plans for the land. Turning a base into a factory, for instance, would require less cleanup than making the installation into a park.

"It really depends on if we make it National Park Service-clean," the official said.

The services already have been through an intense round of budget cuts, with officials from Rumsfeld's office hoping to drastically cut and scale back major military programs through 2011 as part of a wider effort to trim federal budgets.

Now, they must comb through their budget plans once again, attempting to find excess money in their projected accounts.

The goal, the official said, is to take the money "from wherever is the least painful place to take it at the time."

A Pentagon spokesman said he had no information about funding the services would have to put forth to pay for BRAC.

"If the Army is thinking that they might need something else, that's for them to address," the spokesman said.

Each of the services is "putting things on the table, putting very close guesstimates [together] and trying to crystal-ball it as to what's going to happen not only on BRAC, but on everything," he added.

House Armed Services Readiness Subcommittee Chairman Joel Hefley, R-Colo., said the panel is waiting to see how much BRAC ultimately will cost.

"We are keeping watch over it," he said. "If more money is necessary to close bases, we'll put more money in."

Hefley, who initially opposed this BRAC, added that base closings should be funded out of savings the Pentagon has generated in previous rounds in the 1990s. The Pentagon, Hefley said, is "still realizing" the extent of those savings.