Image caption Rebels in Libya have cheered US involvement

The US administration is examining the legality of continuing in the Nato-led Libya campaign beyond Friday.

The War Powers Resolution, passed after US withdrawal from the Vietnam War, rules that involvement in combat operations unauthorised by Congress must be terminated after 60 days.

That deadline is on Friday and deputy secretary of state James Steinberg has said the government is aware of it.

"President Obama has been mindful of the War Powers Resolution," he said.

In reference to the deadline, he said the administration was "actively reviewing" its role.

The president formally informed Congress of US involvement in Libya on 21 March.

White House lawyers are reportedly looking at ways US action in Libya can continue without contravening the resolution.

But Bruce Ackerman, a law professor at Yale University, says continuing without Congressional consent sets a dangerous precedent.

"A future president not as reasonable as President Obama is going to use this case to engage in something much more ambitious.

"From the point of view of long-term constitutional development, this is an important decision which will have precedental force in a very different context."

Congress passed the War Powers Resolution at the end of the Vietnam War, overriding President Nixon's veto.

It built on efforts by the founding fathers to repudiate the model of executive war-making, said Professor Ackerman.