A huge Pentagon spending bill came to the Senate floor already bearing a $453.5 billion price tag. Then concerns about Army combat readiness and security along the Mexican border led lawmakers to add almost $15 billion more.

A vote to pass the bill could come as soon as late Thursday.

With the war in Iraq taking a heavier toll on Army and Marine Corps equipment than had previously been acknowledged — and with Democrats promising to offer a $10.2 billion plan to bolster readiness — Sen. Ted Stevens, R-Alaska, countered with a $13.1 billion plan to provide a down payment on repairing and replacing equipment damaged in harsh conditions in Iraq.

The White House endorsed his move, saying it simply advanced funding for projects it was planning to ask for next spring. But the administration again protested that the Senate Appropriations Committee, in transferring $9 billion for non-defense purposes, had shifted far too much money to domestic programs such as education and senators' favored projects.

The White House said no more than $4 billion should leak from the Pentagon to domestic accounts. That's the funding shift passed by the House.

On Wednesday, GOP border security hawks Jeff Sessions of Alabama and John Kyl of Arizona won approval for $1.8 billion to build 370 miles of triple-layer fencing along the border with Mexico. An additional 461 miles of vehicle barriers would also be built.

That vote came just three weeks after the Senate rejected a plan to add the funding to the Homeland Security spending bill, financed by cuts to other programs. This time, Sessions won a 94-3 vote after adding to next year's estimated $354 billion budget deficit to finance the fence. It's unclear whether the funding will survive House-Senate talks.

The $468.4 billion Pentagon funding bill is only the second of 12 appropriations bills to come to the Senate floor as Majority Leader Bill Frist has given nuts-and-bolts business of the Senate such as spending bills a lesser priority in this election year. Politically nettlesome votes on bills unrelated to defense or homeland security are likely to be delayed until after Election Day.

The addition of $13.1 billion to the underlying defense measure is just a down payment, said Democrats such as Jack Reed of Rhode Island, who said that Army readiness is at its lowest ebb since the post-Vietnam War era.

"There is not a single non-deployed Army brigade combat team in the United States that is ready to deploy," Reed said.

The $13.1 billion comes on top of $50 billion already included in the bill for military operations in Iraq and Afghanistan. All told, the funds brings the tally for the two wars to more than $450 billion, with another installment due early next year.

In trimming funds from President Bush's request for the Pentagon, the bill cuts $250 million from the Army's request of more than $3.5 billion for the Future Combat System, the service's key weapons program. The program is ultimately supposed to cost about $200 billion as it produces a variety of manned and unmanned vehicles, robots and aircraft for 21st century combat.

The bill also cuts $1.3 billion from Bush's $5.3 billion request for the F-35 Joint Strike Fighter, now under development with the help of Britain, because senators believe the technology was premature with testing behind schedule.

All told, the measure trims about $2 billion from Bush's request for procurement funds for various weapons systems. No funding would be provided for KC-135 replacement tanker planes.

The bill would also award a 2.2 percent pay raise for the military.