The monthly cost of the war in Afghanistan, driven by troop increases and fighting on difficult terrain, has topped Iraq costs for the first time since 2003 and shows no sign of letting up.

Pentagon spending in February, the most recent month available, was $6.7 billion in Afghanistan compared with $5.5 billion in Iraq. As recently as fiscal year 2008, Iraq was three times as expensive; in 2009, it was twice as costly.

The shift is occurring because the Pentagon is adding troops in Afghanistan and withdrawing them from Iraq. And it's happening as the cumulative cost of the two wars surpasses $1 trillion, including spending for veterans and foreign aid. Those costs could put increased pressure on President Obama and Congress, given the nation's $12.9 trillion debt.

"The overall costs are a function, in part, of the number of troops," says Linda Bilmes, an expert on wartime spending at Harvard University. "The costs are also a result of the intensity of operations, and the number of different places that we have our troops deployed."

Obama made clear Wednesday that the U.S. role in Afghanistan would remain long after troops are withdrawn, a process planned to begin in July 2011. "This is a long-term partnership," he said during a news conference with Afghan President Hamid Karzai.

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