Washington ? The White House is ready to ask Congress for more money for President Bush’s plan – already hotly debated – to send 21,500 new combat troops into Iraq.

The move would pay for support personnel and otherwise update last month’s request for the Iraq war. It probably will draw criticism from Democrats who say the Pentagon had low-balled estimates of the costs of Bush’s plan for improving security in Baghdad and Anbar province.

The latest request could come as early as today, modifying last month’s $93.4 billion request for military operations in Iraq and Afghanistan through Sept. 30.

Though the changes may be relatively modest, they nonetheless are embarrassing to the White House and the Pentagon, which earlier dismissed criticism from lawmakers that the original $5.6 billion estimate for the troop buildup was too low.

Deputy Secretary of Defense Gordon England told the Senate Budget Committee last week that about 6,000 additional support personnel – such as headquarters staff, military police, and medical personnel – would be needed to complement the 21,500 additional combat troops.

Hours after England testified, White House Chief of Staff Joshua Bolten paid a rare visit to the Capitol to press Senate GOP leaders for the additional money.

The modified request was being finalized Monday, said administration and congressional aides. In addition to the money for increased troop strength, the White House will press for more dollars to battle the Taliban’s resurgence in Afghanistan and get mine-resistant vehicles.

The request probably will come to about $2 billion. It will be accompanied by equal-sized reductions to elsewhere in the larger request, which contained money for two next-generation Joint Strike Fighters and a V-22 tilt rotor aircraft.

At the same time, lawmakers have signaled they will provide an additional $3 billion to put in place the latest round of military base closings. The military base money – cut from the president’s budget when Democrats pushed through a huge spending bill last month – has the strong support of the administration.

In addition to concerns about Bush’s plan to send more troops to Iraq, Democrats say the Pentagon has underestimated the cost of the new mission. The $5.6 billion price covers deployment of combat troops through Sept. 30.

Typically, it takes 5,500 support troops for a 4,000 combat brigade, according to the Congressional Budget Office. But the Defense Department says the most recent addition of troops will require far fewer support troops because a sizable support infrastructure is in place in Baghdad and Anbar province.

Democrats are looking at the must-pass supplemental spending bill as a way of attaching their domestic initiatives. They include farm disaster aid, money for a children’s health insurance program and improvements to levees around New Orleans.