The Libyan regime is "on the back foot", Defence Secretary Liam Fox has declared amid fears of a stalemate in the military action.
Dr Fox struck an optimistic note after almost three hours of talks at the Pentagon with US counterpart Robert Gates which included detailed discussion of the situation.
It came hours after Foreign Secretary William Hague cautioned Cabinet colleagues that despite some progress by the Nato-led mission, the UK should be braced for a "long haul".
The head of the UK's armed forces, General Sir David Richards, also took part in the US talks along with his opposite number Admiral Mike Mullen.
It was Admiral Mullen who warned at the weekend that the United Nations-backed action to end the brutal repression of the rebellion was "moving towards a stalemate".
America has moved to a backseat role in the action although within recent days it has deployed unmanned armed drones as part of the air strike capability.
Dr Fox told reporters: "We have seen some momentum gained in the last few days. We are very grateful to the United States for making the armed Predators available.
"We have seen some progress made in Misrata and it is very clear that the regime is on the back foot. The sooner that Colonel Gaddafi recognises that the game is up - either today or shortly - the better. He is a liability for his people and his country and the sooner he gets this message the better."
Dr Fox hit out at the use of young mercenaries by the regime, which he said symbolised its "desperation".
