WASHINGTON — A key US Senate panel voted Tuesday to authorize limited US strikes on Libya as part of a NATO-led campaign against Libyan strongman Moamer Kadhafi but to forbid the deployment of ground troops.

The Senate Foreign Relations Committee's 14-5 vote set the stage for what was sure to be a volatile full Senate debate as early as this week, with lawmakers deeply divided on whether President Barack Obama's Libya policy flouts US law.

The panel heard earlier from US State Department legal adviser Harold Koh, who argued Obama's approach did not violate the US Constitution or the 1973 War Powers Resolution that aims to constrain presidential war-making authority.

"This administration is acting lawfully, consistent with both the letter and spirit of the Constitution and the War Powers Resolution," said Koh, who allowed that consultations and communications with the congress could have been better.

The panel acted days after the US House of Representatives defeated a bill to authorize US operations against Libya and rejected another measure that would have cut funding for direct US combat strikes on Libyan targets.

Opposition to Obama's Libya policy, fueled by polls showing it is broadly unpopular with the US public, remained fractured and unlikely to settle on a strategy that could ultimately force the president to change course.

The resolution that cleared the committee restated Obama's goal of toppling Kadhafi and greenlighted US contributions to the military effort for one year or for the duration of NATO operations.

The committee beat back by 14-5 margin an amendment by Republican Senator Richard Lugar -- once Obama's foreign policy mentor -- to end US air strikes and drone attacks and limit the US military to supporting NATO with intelligence sharing, refueling, search and rescue assistance, and operational planning.

Lugar won approval of other amendments, including a prohibition on sending US ground troops into Libya and a message that the Libyan people and Arab League nations that urged US intervention should pay for reconstruction costs.

At his urging, the panel approved an amendment flatly rejecting the White House's legal argument that US forces are not engaged in "hostilities" and that the War Powers Resolution therefore does not apply.

The panel approved an amendment by Democratic Senator Jim Webb prohibiting the president from sending grounds forces or contractors into Libya to take on post-Kadhafi roles like peacekeeping.

Democratic US Senator John Kerry -- who chairs the committee and crafted the measure with veteran Republican Senator John McCain -- told AFP he hoped the full Senate might act as early as this week on the resolution.

The panel's vote came after lawmakers grilled Koh on whether Obama had violated the 1973 law, which requires US presidents to secure permission from Congress for military deployments lasting more than 60 days.

Koh restated the administration's argument that the act does not apply because US forces are not engaged in "hostilities" as defined by the law, but said "reasonable minds can certainly differ."

And "we acknowledge that there were perhaps steps we should have taken or could have taken to foster better communication on these very difficult legal questions," Koh added.

Lugar cited news reports according to which US warplanes struck Libyan air defenses some 60 times since NATO took over the lead for operations at the end of March, while unmanned Predator drones have fired missiles on 30 occasions.

"If the United States encountered persons performing similar activities in support of Al-Qaeda or Taliban operations, we certainly would deem them to be participating in hostilities against us," he said.

Koh argued that the fact that there were no US forces on the ground and that there was a low risk of escalation or US casualties meant that US involvement did not rise to the level of "hostilities."

"By that reasoning, we could drop a nuclear bomb on Tripoli and we would not be involved in hostilities," countered Republican Senator Bob Corker.

Corker accused the administration of "basically sticking a stick in the eye of Congress" by not securing its authorization for the conflict.

"That was not our intent. And if you felt that a stick was stuck, that was not the goal," said Koh.