The United States has stopped short of granting full diplomatic recognition to Libya's rebel council, but the White House has said the council is a "legitimate and credible interlocutor of the Libyan people".
Mahmoud Jibril, who serves as the foreign minister of the rebels' National Transitional Council (NTC), met Tom Donilon, the US president's national security advisor, at the White House on Friday.
"During the meeting, Mr Donilon stated that the United States views the [NTC] as a legitimate and credible interlocutor of the Libyan people," the White House said in a statement released after the meeting.
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"In contrast, Mr Donilon stressed that [Libyan leader Muammar] Gaddafi has lost his legitimacy to rule and reiterated [US] President [Barack] Obama's call for Gaddafi to leave immediately," it said.
Obama did not meet with the opposition leaders.
"Mr Donilon and Dr Jibril discussed how the United States and the coalition can provide additional support to the [NTC]. Mr Donilon applauded the [NTC's] commitment to an inclusive political transition and a democratic future for Libya," the statement concluded.
The recognition stops short of what the NTC had sought. In an op-ed published in the New York Times ahead of his meetings in Washington, Jibril had written that the NTC was seeking to be recognised as the "sole" legitimate representative of the Libyan people.
The White House, however, has signalled that such a move would be premature.
"I don't anticipate action like that," Jay Carney, the White House spokesman, said.
Meanwhile, the US has stepped up financial assistance for the anti-Gaddafi rebels, with Obama authorising $25m in non-lethal assistance and $53m in humanitarian aid.
The White House said it was looking for ways to increase financial support to the opposition, in part through congressional legislation that would free up a portion of the more than $30bn in frozen assets connected to the Gaddafi government in US banks, so that it could be used to aid the rebels.
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"We believe that if we could access and use blocked government of Libya assets it could make a significant amount of money available to alleviate the suffering of the Libyan people," Carney said.
The rebels have said they need up to $3bn in the coming months for military salaries, food, medicine and other supplies. They also say no country has sent the arms they need.
"If there is any country that is willing to arm us, we are happy to defend ourselves," Ali Tarhouni, the council's minister of finance and oil, said after a meeting at the State Department on Friday.
"This is a thug, a killer regime that took a peaceful movement and forced us to carry arms. It's legitimate that we have arms to defend ourselves."
Despite financially backing the opposition, the White House says questions about who exactly the rebels are and their long-term objectives are keeping the United States from recognising the council as the legitimate Libyan government.
"The question of recognition is one of many policy issues still under review," Carney said.
Friday's meetings came as a deadline neared on a 60-day window Obama has to keep the US military involved in the Libya campaign without congressional approval.
However, the White House said the United States and NATO will continue military operations in Libya as long as Gaddafi continues to attack his people.
The White House spokesman offered no specifics on how the US planned to do that, saying only that officials were, "in regular communications with Congress, and that will continue".
Administration officials have been eager to show signs of progress in the Libyan bombing campaign, first led by the US and now overseen by NATO.
Obama on Friday met privately with Anders Fogh Rasmussen, the NATO Secretary-General, in the Oval Office. The White House said the two agreed that military action would go on until Gaddafi's assault on civilians had stopped.
NATO has been intensifying airstrikes in several areas of Libya against Gaddafi's troops in a bid to weaken his campaign against the rebel uprising.
The Libyan leader, in an audio message broadcast on state television on Friday, said he had survived the assault.
Hours after Gaddafi's minute-long speech, the sound of four explosions, most likely a NATO strike, could be heard in Tripoli.
Government spokesman Ibrahim Uthman said the strikes targeted the country's Agriculture Ministry. The same building, however, was targeted days ago and, at the time, residents said it was a government intelligence building.
Shortly before Gaddafi's remarks were broadcast, regime spokesman Moussa Ibrahim claimed that a NATO airstrike in Brega had targeted a meeting of dozens of clerics and officials from around Libya, a claim NATO denies.
Ibrahim said 11 imams were killed in their sleep at a guesthouse, and 50 people were wounded, including five in critical condition.
The alliance, responding to the claim, said it had attacked a military command-and-control centre, and that it could "not independently confirm the validity" of claims of civilian casualties.
"We're very careful in the selection of our targets and this one was very clearly identified as a command center," said an official at NATO's operational headquarters in Naples, Italy, who spoke under the alliance's rules that he could not be named.
Source: Al Jazeera and agencies