Secretary of State Hillary Rodham Clinton, meanwhile, held talks in London with an envoy from the Libyan political opposition group trying to overthrow Moammar Gadhafi.
In Washington, under questioning by Congress, NATO's top commander, U.S. Navy Adm. James Stavridis, said officials had seen "flickers" of possible al-Qaida and Hezbollah involvement with the rebel forces. But Stavridis, testifying on Capitol Hill in Washington, said there was no evidence of significant numbers within the political opposition group's leadership.
The Navy Tomahawks targeted storage sites for surface-to-surface missiles near the Libyan capital, while combat aircraft of the U.S. and its partners in an international air campaign struck at ammunition storage depots and other military targets in western Libya. The rebels, though, were reported in full retreat after trying to march on Sirte, a city about halfway between Tripoli and the de facto rebel capital of Benghazi.
All 22 Tomahawks were launched from the USS Barry, a guided missile destroyer in the Mediterranean, according to a U.S. defense official. It was the highest number of Tomahawks fired in several days, even as the Navy has reduced the number of missile-firing ships and submarines off the coast and as the U.S. has prepared to give NATO full control of the Libya campaign.
The Libyan missiles targeted by the U.S. onslaught could have been used by pro-Gadhafi forces defending Tripoli, should heavy combat spread to the capital, which remains under Gadhafi's control. The rebels are outmatched in training, equipment and other measures of military might by Gadhafi's remaining forces, and would be hard-pressed to mount a full-scale battle for Tripoli now.
As for the overall international campaign against Gadhafi, Stavridis said he expected a three-star Canadian general to assume full NATO command of the operation by Thursday. Meanwhile, the Pentagon put the price tag for the war thus far at $550 million.
Clinton told reporters in London that the U.S. is operating with incomplete information about the Libyan opposition. But she said there was no information about specific individuals from terror organizations that are part of the political opposition.
"We're building an understanding, but at this time obviously it is, as I say, a work in progress," she said. "We don't know as much as we would like to know and as much as we expect we will know."
The Obama administration is not ruling out a political solution in Libya that could include Gadhafi leaving the country, she said, but she acknowledged there is no timeline.
Clinton met with Mahmoud Jibril, a representative of the Libyan political opposition.
"Their commitment to democracy and to a very robust engagement with people from across the spectrum of Libyans is, I think, appropriate," she said.
A senior administration official said the U.S. will soon send an envoy to Libya to deepen relations with leaders of the rebels. But the official, who spoke on condition of anonymity to discuss internal planning, said the meeting wouldn't constitute formal recognition.
Chris Stevens, who until recently was the deputy chief of mission at the now-shuttered U.S. Embassy in Tripoli, will make that trip.
White House spokesman Jay Carney said that the opposition leaders Obama officials have met with have expressed views that correspond with U.S. goals.
"We've spent a lot of time looking at the opposition and now meeting with opposition leaders," Carney told reporters. "The folks who were in London, the leaders that Secretary Clinton met (previously) in Paris have made clear what their principles are. And we believe that they are meritorious."
"That doesn't mean, obviously, that everyone who opposes Moammar Gadhafi in Libya is someone whose ideals we could support," Carney said.
The pace of air strikes by the U.S. and its international partners has picked up in recent days. The Pentagon said there were 119 strikes on Monday, up from 107 on Sunday and 88 on Saturday.
Clinton said international leaders have made no decisions about arming the rebels, but they talked at a London conference on Tuesday about providing non-lethal assistance including funds to keep them going. In his speech to the nation on Monday, Obama pledged that $33 billion in Libyan government funds frozen by the U.S. Treasury would at some point be made available to the Libyan people.
Obama said the U.S. was stepping back from the lead military role in Libya, although the extent of future participation remained unclear.
The president, meanwhile, continued to take political heat for his approach, with Republicans leading the criticism.
They vowed to press senior administration officials for greater clarity at closed briefings slated for Wednesday. Clinton, Defense Secretary Robert Gates and Joint Chiefs of Staff Chairman Adm. Mike Mullen are to brief members of the House and then meet with members of the Senate.
"The president's remarks were a step in the right direction. They didn't answer every question, but we'll continue to pose those to Secretary Clinton and Secretary Gates," Senate Republican Leader Mitch McConnell of Kentucky told reporters.
Obama received strong backing for his efforts in Libya from his 2008 presidential rival - Republican Sen. John McCain of Arizona.
"The president's decision to intervene in Libya deserves strong bipartisan support in Congress" and in the country, McCain said in a speech on the Senate floor.
"We have prevented the worst outcome in Libya but we have not secured our goal," he said, stressing that Gadhafi must go.
Rep. Howard "Buck" McKeon, R-Calif., chairman of the House Armed Service Committee, said Obama needs to further refine U.S. purposes.
"I still did not hear a clearly defined goal for how long military operations will last in Libya," McKeon said. "Utilizing U.S. warriors to protect civilians from a brutal dictator is a noble cause, but asking them to maintain a stalemate while we hold out hope that Gadhafi will voluntarily leave his country raises serious questions about the duration of the mission."
Associated Press writers Lolita C. Baldor, Donna Cassata, Pauline Jelinek and Jim Kuhnhenn contributed to this report.