Appearing before the U.S. Senate's Foreign Relations committee, the U.S. State Department's legal adviser argued that President Barack Obama has acted within the law despite failing to get Congressional approval for the campaign in Libya.

The War Powers Act of 1973 established that the president must withdraw American forces from hostilities after 90 days if Congress does not approve the military action. The conflict in Libya has exceeded that limit, but State Department legal Adviser Harold Koh stressed repeatedly that the limited scope of American operations in Libya did not rise to the level of hostile actions.

This administration is acting lawfully consistent with both the letter and spirit of the constitution and War Powers Act, Koh said. The situation in Libya does not constitute a war requiring specific Congressional approval.

Koh maintained that Libya represents a virtually unique situation in relation to past conflicts given the lack of casualties or exposure to harm for U.S. forces, the fact that U.S. involvement is likely to escalate and the limited role American troops are playing in supporting NATO. He warned against interpreting the War Powers Resolution too rigidly.

'Hostilities' is an ambiguous term of art that is defined nowhere in the statute, Koh said, underlining that the standard has never been defined by Congress or the courts and charging that the architects of the War Powers Act declined to give it further meaning to avoid hampering future presidents.

Obama has faced mounting Congressional resistance on Libya. The House rebuked Obama on Friday with a non-binding vote to restrict funding for the operation, and his decision to bypass the counsel of legal advisers and continue the operation has fueled criticism of what some see as his overstepping his authority.

Sen. Dick Lugar, R-Ind., sharpened those critiques, saying before Koh spoke that Obama made a deliberate decision not to seek congressional approval and chiding the president for a lack of constitutional principle. He also cited Obama's apparent reversal from his 2007 statement that, The president does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation.

Obama's actions are a fundamental failure of leadership that placed expedience before constitutional obligations, Lugar said, adding that the president's highly dubious arguments...break new ground in justifying unilateral approval of force.

The hearings occured as the Senate works on a resolution to approve the intervention in Libya.