US officials have met with representatives of Muammar Gaddafi to deliver a message that the embattled Libyan leader must go, a state department spokesperson said.
The rare meeting between US diplomats and Gaddafi envoys on Saturday was held "to deliver a clear and firm message that the only way to move forward is for Gaddafi to step down," the official said on Tuesday.
"This was not a negotiation. It was the delivery of a message," the official said in a statement issued in New Delhi, where Hillary Clinton, the US secretary of state, is on an official visit.
The meeting involved assistant secretary of state Jeff Feltman and two other American officials, said a senior US official, who declined to say who represented the Gaddafi government or where the meeting occurred, although he said it was not in Libya.
A State Department official told CNN that the meeting had taken place in Tunis, the Tunisian capital, and had lasted three hours.
The official said the meeting had been initiated by the US following contact by senior Libyan officials which had indicated Tripoli believed Washington's commitment to Gaddafi's departure from power was less firm than its international allies.
"Senior officials in the Gaddafi regime had over a period of weeks made repeated calls to senior officials in the U.S. and in those conversations they evinced an incorrect sense that somehow the United States was in a different place from other members of the international community and that the U.S. could see a future for Gaddafi in Libya," said the official.
The meeting followed Washington's decision on Friday to formally recognise the Benghazi-based rebel National Transitional Council as the legitimate interim government of Libya at a Contact Group meeting in Turkey.
Libya's government confirmed on Monday it had held talks with US officials and welcomed discussions but only without preconditions.
"We support any dialogue, any peace initiative as long as they don't decide Libya's future from without, they decide it from within," Libyan government spokesman Ibrahim Moussa told journalist in Tripoli.
"If any country involved in this aggression against us wants to revise its position and genuinely wants peace and democracy in Libya, come to us and we will discuss everything, but do not condition your peace talks. Let Libyans decide their future."
The US is among countries contributing to a NATO-led bombing campaign sanctioned by the United Nations to prevent civilians from attack by Gaddafi forces.
The operation has also allowed rebels to make advances in their campaign to overthrow Gaddafi, who has ruled Libya since 1969.
On Monday rebels claimed they had regained control of the key oil town of Brega, 750km east of Tripoli, which has changed hands several times since fighting began in February.
South of Tripoli, rebels also control the village of Qwalish, just 100km south of Tripoli, which allows opposition fighters access to the highway running north to the capital.
Recognition of the NTC as Libya's legitimate government has been condemned by Russia which criticises the US and other countries for taking sides in a civil war.