It seems like simple arithmetic. To send 30,000 U.S. troops to Afghanistan, with each troop costing about $1 million, the United States has to spend $30 billion.

But at the intersection of war, money and politics, nothing is simple. The cost of the supplemental funding bill to fund the war in Afghanistan was inflated, a recent congressional report and several military budget experts said.

The U.S. Senate approved a supplemental appropriation bill that included $33 billion in war funding, $30 billion of which would finance the surge in Afghanistan that would increase the number of U.S. troops in the country to almost 100,000 by September.

The bill is an addition to the $130 billion in the 2010 budget for the wars in Iraq and Afghanistan. President Barack Obama announced plans for the surge last December, too late to add the money into the 2010 budget.

The bill was returned to the Senate after last week's vote in which the House of Representatives tacked on more money before approving it. With lawmakers on break, final approval won't happen next week at the earliest. The House didn't make changes to the war funding portion of the legislation.

The additional war funding is intended to pay for deploying another 30,000 troops to Afghanistan but some budget experts have questioned the accuracy of cost estimates for the surge.

The Congressional Research Service, the research arm of the U.S. Congress, reported that Defense Department estimates are so high that, if it were to use all the funding it asked for in 2010, including the supplemental war bill, it would have to more than double its spending for Afghanistan. From October 2009 through February 2010, the Department of Defense spent less than one-quarter of its funding for the entire 2010 fiscal year, the report said.

In a letter to the House Committee on Appropriations last January, the Congressional Budget Office estimated the surge for would require an additional $13 billion in 2010, and increased funding through 2013. The CBO estimates the cost per troop in the surge is about half the Defense Department's $1 million projection.

Experts caution that the cost-per-troop calculation is a difficult one but they suggest there are ways to pay for the surge other than supplemental appropriation bills, which are reserved for emergencies and unanticipated costs. The military has a backlog of unspent money that it can use pay for some of the expenses in the war bill, experts say.

"They are spending out at a slower rate than anticipated, so that means they have that the funds to tie them over," said Gordon Adams, professor of international relations at American University and an expert on defense policy and national security budgets.

As of February, the Defense Department had $6.4 billion available from 2009 and 2010 that it could use to train Afghan security forces, CRS said. The new war funding bill includes $2.6 billion for training.

Adams said the military's ramped up efforts to train Afghan forces are consistent with the U.S. exit strategy, which includes building up a security force that can take over when the U.S. beings troop withdrawals in July 2011.

However, CRS reports that the Defense Department would have to almost triple its monthly spending to deplete its coffers by October. Add on $2.6 billion and it would have to increase spending by almost seven times, to $2.2 billion a month, for the next two months.

The report also identifies $4.7 billion in the supplemental funding bill that should have been requested in the regular 2011 defense budget because it doesn't qualify as emergency spending -- $1 billion to train Iraqi forces, $2 billion for fuel costs and $1.7 billion to fix or replace equipment.

Todd Harrison, a defense budget expert at think tank Center for Strategic and Budgetary Assessments, said the requests reflect poor planning by the Defense Department.

The supplemental war bill would bring spending on the war in Afghanistan since 2001 to $314 billion. Of the $159 billion requested in the fiscal 2011 budget, $114 billion would go toward Afghanistan, the Department of Defense said.

Emergency or supplemental appropriations have been the primary means of funding the wars in Iraq and Afghanistan, a source of contention throughout the George W. Bush administration. However, defense experts agree that the latest bill is a more appropriate use of the funding. More money was needed, and quickly, to support the new strategy for Afghanistan, experts said.

"This is exactly what supplemental appropriations are for," Harrison said.

Added Adams, "If you're going to change the policy, you're going to have to fund it some way."

Lawmakers on both sides of the aisle agree, and have overwhelmingly supported the bill. Even House Appropriations Committee Chairman Rep. Dave Obey, D-Wis., a long-time war opponent, supported funding for the surge despite his concerns with the strategy in Afghanistan.

Although the Obama administration has made an effort to be more transparent with war funding outside the regular budget, it hasn't managed to do away with supplemental appropriations altogether, which has drawn criticism from war opponents.

"I'm not sure that war funding ever gets the scrutiny it ever needs to get," said Laicie Olson, senior political analyst for Washington's Center for Arms Control and Non-Proliferation. "War funding is sort of a no-brainer in this Congress."