The Pentagon has ruled out sending ground troops to Libya and reiterated that any change in the leadership would be determined by the people of the country and not by any external forces.

"The President from the very outset of this operation had made clear that we were going to conduct this without putting US military boots on the ground. That has been the starting point. It remains the guiding principle here," Geoff Morrell, Pentagon spokesman told reporters.

"The fact of the matter is, US military boots on the ground are prohibited by the President of the US in Libya. That is just the way it is, and I don't foresee that changing.

"Obviously the commander-in-chief is within his right to adjust to situations, but as the (Defense) Secretary told the Congress last week, he does not anticipate that changing," he said.

With regards to whether or not other assistance is being contemplated for the rebels in Libya, no decision has been made yet on arming the rebels.

"I think the (Defense) Secretary made it clear what his preference is with regards to that, that is the course of action that the alliance chooses, the coalition chooses to pursue, that it be done by others, given all that is currently on our plate," he said.

"Right now, the focus, primarily in terms of the interagency discussions on this matter, is what kinds of support we could provide in a nonlethal respect for the rebels in Libya. But that's a complicated discussion. It's an ongoing discussion. But I think that's where the focus is, not on reconsidering the boots-on-the-ground decision," he said.

Morrell said the focus over the past couple of weeks has been on the opening phase of engagement, which has relied heavily on American air power, and naval power for that matter.

"Now we're transitioning into more of a support role that has requirements all its own. We've got a heavy commitment of jamming aircraft; of ISR [intelligence, surveillance, and reconnaissance] of all sorts, manned and unmanned; of tankers. So there's a lot that we are contributing to this mission beyond strike sorties and of course, command and control, as well," he said