Libya Price Tag for U.S.: $550 Million So Far, Members of Congress Express Frustration

VIDEO: Footage shows rebels fleeing after ambush by Gadhafi
WATCH Target Libya: Gadhafi Ambushes Rebels

The intervention in Libya has cost the United States $550 million through Monday, and going forward, it will cost an estimated $40 million a month as the United States reduces its role, Defense Secretary Robert Gates said today.

The expense, for now, is coming out of the Defense budget, but Gates said he would eventually like the cost to be included in the next fiscal year's overseas contingency operations bill, which Congress has yet to pass. Gates said doing so would not require raising the top line amount for that funding bill.

The number is slightly lower than the $600 million figure provided by the Pentagon earlier this week.

Obama administration officials today continued to tout coalition efforts and the need for intervention, saying they have successfully degraded Col. Moammar Gadhafi's defense capabilities but not to the point where he can be broken.

"The removal of Col. Gadhafi will likely be achieved over time through political and economic measures, and by his own people," Gates told members of Congress today. "However, this NATO-led operation can degrade Gadhafi's military capacity to the point where he -- and those around him -- will be forced into a very different set of choices and behaviors in the future."

But with millions of dollars being poured into the conflict, members of Congress on both sides of the political aisle have grown increasingly agitated about the mission and endgame in Libya, which has cost the United States millions of dollars.

"It all seems extremely open-ended to me," said Sen. John Cornyn, R-Texas.

Others fear the successes that coalition forces have achieved in the two weeks since the strikes began will be averted because of the lack of U.S. leadership.

"The U.S. military will no longer be flying strike sorties against Gadhafi's ground forces," said Sen. John McCain, R-Ariz., who supports the offensive. "I believe this is a profound mistake with potentially disastrous consequences."

NATO has taken over the day-to-day operations, and the United States will continue to provide some capabilities, such as "electronic attack, aerial refueling, lift, search and rescue, and intelligence, surveillance and reconnaissance support," Gates said.

But the endgame is unclear, and rebels in Libya seem to be losing the momentum they have gained over the past week. Opposition forces have expressed frustration at the lack of airstrikes in cities where Gadhafi's forces quickly outnumber opposition forces.

"If these are not populated areas, what is?" Shamsiddin Abdulmolah, a frustrated opposition council spokesman, told ABC News. "People are wondering where the truth is. ... [Gadhafi forces] will demolish Adjdabiya and bring it down to the ground. If the coalition forces are just going to hang around and let that happen, what's the point of their presence at all? They're saying to Gadhafi go in and do your work."

In the meantime, it is getting increasingly challenging for coalition forces to distinguish rebels from Gadhafi's forces, who are now driving around in the same kind of armed pickup trucks as the opposition.

Rebels also lack a unified command structure and are plagued with problems over control.

Gates today admitted that anti-Gadhafi forces are a disparate group that had emerged spontaneously, rather than as an organized opposition force.

"It is very scattered, and probably each element has its own agenda," he said.

And while the goal of the coalition mission is to not remove Gadhafi from power, Gates said that would be the ideal outcome and that the administration had considered the possibility "of this being a stalemate and a drawn-out affair.

"Unless there's some king of significant change in behavior in terms of his own people, it's hard for me to imagine circumstances in which we would be content to tolerate a government that would have Gadhafi at its helm," he said.

Rep. Walter Jones, R-N.C., expressed frustration at the absence of a defined endgame.

"I get so upset when I hear ... we can't tell you when it's going to end," Jones said. "Gadhafi is absolutely evil, and yet we take the lead on everything. I don't' know where the other countries are. Why in the world don't they take the lead on something?"

President Obama signed a secret presidential finding authorizing covert operations to "aid the effort" in Libya, a source told ABC News Wednesday. While it doesn't direct covert operatives to provide arms to the rebels immediately, it does prepare for such a contingency and other contingencies should the president decide to go down that road in the future.

Gates would not comment on reported CIA activities inside Libya but reiterated that there will be no American boots on the ground.

"Not as long as I'm in this job," he told lawmakers.

Gates said he's not aware of other coalition partners planning to send ground forces.

In the past 24 hours, the United States, NATO and coalition aircraft have flown about 204 sorties, 110 of which were strike-related, hitting fixed and mobile targets in the vicinity of Tripoli, Misurata and Ajdabiyah, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, said today.

He said most of Gadhafi's capability is ground capability, and that the vast majority of his defenses -- at least 20 to 25 percent -- had been destroyed since the coalition began imposing the no-fly zone.

Mullen said the NATO commander, Canadian Lt. Gen. Charles Bouchard, has at his disposal more than 220 aircraft of every size and capability.

Bouchard has said NATO also has 12 ships ready to enforce the naval arms embargo. The organization has conducted 90 flights and sorties since taking over full control earlier this morning.

He also confirmed that NATO is investigating early reports of an air strike in Libya that may have caused 40 civilian casualties.

ABC News' Luis Martinez, Jake Tapper, Martha Raddatz and Alexander Marquardt contributed to this report.