The Pentagon has begun tapping into its $25 billion emergency fund for the Iraq war to prepare for a major troop rotation and intense fighting this fall, administration officials said on Tuesday, despite the White House's initial insistence that it had enough money.

The Pentagon has already used more than $2 billion from what the White House dubbed its "contingency reserve" fund for Iraq. The money is being used to ramp up production of armored Humvees to support the troop rotation, as well as to buy body armor and bolster fuel supplies, the officials told Reuters.

The decision to use the $25 billion in Iraq reserves underscores concern within the administration about the rise in anti-American violence in Iraq.

The decision follows last week's announcement that President Bush plans to divert nearly $3.5 billion from Iraqi water, power and other reconstruction projects to improve security.

The White House had initially asserted it would not need additional war funding until January or February, 2005 -- well after the November presidential election.