President Barack Obama insisted Wednesday that the current US action in Libya did not violate US law, rejecting rising criticism in Congress over the legal grounding and goals of the operation.

In a 30-page report to Congress, the White House argued that the current US mission in the NATO-led assault on the forces of Moamer Kadhafi did not require congressional authorization as Washington was confined to a supporting role.Senior Ob
ama aides said the US involvement in the UN-authorized operation to protect civilians did not rise to the kind of direct, offensive warfare that needed to be endorsed by lawmakers under the 1973 War Powers Act.

"We are not engaged in any of the activities that typically over the years in war powers analysis has been considered to constitute hostilities within the meaning of the statute," a senior administration official said.

"We are not engaged in sustained fighting, there has been no exchange of fire with hostile forces, we don't have troops on the ground, we don't risk casualties to those troops," the official said on condition of anonymity.

"Within the precedents of a war powers analysis... we are confident we are operating consistent with the resolution."

Senior White House aides said the report, containing the first detailed legal analysis of the US mission, had been sent to Capitol Hill, though sources in House Speaker John Boehner's office said they had yet to receive it.

The report was compiled after Boehner sent a scathing letter to the president warning that US operations would be illegal come Sunday because they lacked formal congressional approval.

Boehner specifically cited the War Powers Act, that gives presidents 60 days to get authorization for a military deployment and, failing that, sets a further 30 days to withdraw them from harm's way.

The administration said that the while it did not believe that it required formal authorization for the Libya operation, it would welcome a statement of support for the mission.

White House spokesman Jay Carney also said that the administration had initiated more than 40 points of contact with Congress, disputing claims that lawmakers had not been sufficiently kept up to speed.

"We believe that the support for the overall mission, the support for the goal of protecting Libyan civilians and holding Colonel Kadhafi accountable will continue," Carney said.

"It is support that we've had from Congress in the past, and we expect it to continue, because now is not the time to send mixed messages, as we've had the success that we've had in that mission."

Political maneuvering in Washington over Libya took place as western officials insisted their intervention was working and could be sustained, and as rebels made advances on the road to Tripoli.

But after 10 weeks of air strikes against Kadhafi's forces and defections from his regime, it remained unclear how long the Arab strongman could last out, and whether the NATO-led mission would dislodge him.

In another sign of angst in the Capitol over the mission, anti-war Democratic lawmaker Dennis Kucinich and a bipartisan group of nine other lawmakers filed a suit alleging Obama bypassed Congress in ordering the mission.

"Neither NATO nor the UN trump the Constitution of the United States," Kucinich said, adding later on CNN: "If it looks like a war, it's a war."

Washington took a prime forward role in Libya after the UN Security Council passed a resolution on March 19 allowing for air strikes against Libyan regime forces in order to protect civilians.

But aides said that Obama was good to his word and pulled US forces back into a support mission after an initial blitz of airstrikes and the operation is now under NATO command with Britain and France the most active members.

Senators and representatives have also expressed concerns about how long the conflict against Kadhafi is taking, its impact on the turmoil in the Middle East and on US standing in the Muslim world.

But another senior US official told reporters on Wednesday that the mission was going well, and had yielded important successes, and argued that Obama's decision to launch military action had prevented a feared civilian massacre.

"The bottom line is that lives have been saved; Kadhafi's advances have been stopped, the opposition and the Libyan people have had time and space to organize," the official said.

"Right now we see a situation in which time very much is working against Kadhafi.