US senator John McCain has called on the US to recognise Libyan rebels as the true voice of the Libyan people and transfer frozen assets to them.
He was speaking to reporters during a visit to the rebel stronghold city of Benghazi, in the east of Libya.
Senator McCain also called for NATO to step up its air strikes against forces loyal to the Libyan leader, Muammar Gaddafi, and said coalition countries should provide rebels with weapons and training.
Mr McCain, believed to be the first US politician to visit Benghazi since the conflict broke out in late February, made the trip to Libya on his own.
The US Treasury has frozen more than $US34 billion in Libyan government assets thus far of sanctions aimed at putting pressure on Colonel Gaddafi's regime.
Earlier, the head of the US armed forces warned that the conflict in Libya is moving towards stalemate.
Admiral Mike Mullen coalition air strikes against Libyan ground troops have reduced their capability by more than 30%.
Even so, the war is moving towards stalemate because neither the Libyan army nor the rebels can land knockout blows.
The US has authorised the use of armed, unmanned Predator drones over Libya to give "precision capabilities".