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Obama said Saturday in his weekly radio and Internet address that international forces are succeeding in their mission in Libya. He also said Libya's air defenses have been "taken out" and forces loyal to Muammar al-Qaddafi have been pushed back from cities where the people have risen up against him.

President Obama will address the nation Monday night on the crisis in Libya in an effort to clear up questions regarding the U.S.'s handling of the crisis.

Lawmakers have criticized the president for not consulting with them sufficiently before launching military attacks against Qaddafi's forces and several of them have raised concerns over the cost of funding military efforts. Congressional leaders also say Obama has failed to lay out clear goals for the mission.

The speech announcement came as Pentagon officials said they were considering additional firepower and airborne surveillance systems to attack and find enemy troops in Libya, who are still considered threats to civilians.

Obama will speak at 7:30 p.m. ET at the National Defense University in Washington, the White House said Friday.

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While the U.S. is eager to take a backseat role in the international military campaign in Libya, it is considering stepping up its assistance to rebel forces through humanitarian, political, economic and even military aid, a U.S. official said Friday.

"Nothing is off the table right now," Gene Cretz, a U.S. ambassador to Libya, said at a news conference.

But Cretz wouldn't provide details.

"I'm not going into any internal discussions we are having about whether we will provide arms or whether we won't provide arms," he said. "I can just say that the full gamut of potential assistance we might offer both on the non-lethal and the lethal side is a subject of discussion within the U.S. government, but there has been no final decision made on any aspect of that."

Cretz's comments came a day after NATO agreed to take control of the almost week-old no-fly-zone. White House Press Secretary Jay Carney said Friday that transfer of command and control of the no-fly zone over Libya to NATO will be complete in a couple of days, and by early next week the rest of the U.N.-authorizied mission.

But NATO's decision doesn't allow America to swiftly move into the supporting role the Obama administration prefers.

American sea and airpower remain key parts of the effort to keep Qaddafi forces from attacking civilians after allies balked at assuming complete command of the campaign that began six days ago. The U.S., France and Great Britain maintain primary responsibility for attacks on Qaddafi's ground forces and air defense systems, which are the toughest and most controversial parts of the operation.

Carney said that agreement had been reached on a political level for NATO to assume control of the entire mission but that the military plans associated with that were being worked out.

Obama updated congressional leaders on the situation in a conference call Friday.

The president told lawmakers on Friday that American involvement in Libya will be ratcheted down and emphasized that it is not an American-led effort, a senior Republican aide told Fox News. The president also said there is not a clear endgame on how to remove Qaddafi from power.

Republicans were still dissatisfied after Friday's meeting.

"The speaker appreciates the update today, but still believes much more needs to be done by the administration to provide clarity, particularly to the American people, on the military objective in Libya, America's role and how it is consistent with U.S. policy goals," a spokesman for House Speaker John Boehner said.

U.S. officials have struggled to answer difficult questions about the rules of engagement in Libya.

Asked about reports that rebel forces were detaining suspected Qaddafi loyalists, Cretz said, "I don't have any information about that."

Earlier in the week, White House National Security Adviser Tom Donilon said the coalition forces are treating the rebels as civilians, even though they're in an armed struggle against the Qaddafi regime.

"They're not military forces under the direction and control of Qaddafi," he said.

Cretz said Friday the U.S. is "gradually stepping up its contacts on a daily basis" with the rebel forces that have formed the opposition government.

While the U.S. still hasn't formally recognized the legitimacy of the opposition, Cretz said an envoy will soon deploy to the rebel stronghold of Benghazi.

Obama, already prosecuting wars he inherited in Iraq and Afghanistan, has been eager to limit U.S. involvement in Libya and quickly hand off control, but disagreements among NATO countries have complicated that.

Obama had said the U.S. lead role in subduing Qaddafi's forces would be a matter of days, not weeks, and then the handoff of control would occur. Carney said Friday the president was delivering on that.

"He said what he would do, and he's doing what he said," said Carney.

"What we will not be is in the lead either in the no-fly zone or the civilian protection."

The Associated Press contributed to this report.