The US State Department has said American officials met representatives of Colonel Gaddafi's government at the weekend to insist that the Libyan leader must give up power.
A spokesman said the meeting, which involved US diplomats, was held at an undisclosed location on Saturday.
He said the US side delivered a clear and firm message that the only way to free Libya from war was for Colonel Gaddafi to step down.
The secret meeting occurred as Libyan government forces fought rebels for control of the oil port of Brega. Insurgents yesterday claimed they had surrounded the city in what would be a major boost to their campaign.
Libya said it welcomed discussions but only without preconditions.
'Any dialogue with the French, Americans, British is welcome,' government spokesman Ibrahim Moussa told journalists in Tripoli.
'We will discuss everything, but do not condition your peace talks. Let Libyans decide their future.'
Secretary of State Hillary Clinton announced US recognition of the rebels on Friday, a major diplomatic step that could unblock billions of dollars in frozen Libyan funds.
Brega has changed hands several times in the back-and-forth fighting along Libya's Mediterranean coast since the rebellion began in February.
Libyan TV, in a bid to counter the rebel claims, showed what it said was footage taken yesterday of ordinary life in Brega, with students taking an exam and workers at a natural gas plant.
Col Gaddafi is refusing to step down despite the rebellion, NATO air strikes and defections of members of his inner circle.
On Saturday - as his envoys met US officials - he called rebels traitors and said he had no plans to leave the country.
