Jalal al-Gallal from the National Libyan Transitional Council has told the CA there has been no direct contact with the Gaddafi regimen.
Forces loyal to Libyan leader Col Muammar Gaddafi have launched further air strikes on the rebel-held oil port of Ras Lanuf, in a renewed offensive.
Warplanes fired missiles on residential areas and near rebel positions in the desert, witnesses said.
There were no reports of casualties.
Meanwhile, the rebels said they had been approached by pro-Gaddafi officials offering to hold talks on an exit for the Libyan leader.
The rebels rejected the offer, a spokesman said.
The Libyan leader had not sent anyone himself, but lawyers from Tripoli had volunteered to act as go-betweens, Former Justice Minister Mustafa Abdel Jalil, who heads the rebels' Transitional National Council, told AFP.
Col Gaddafi has refused to cede power in the past, arguing that he has no official position and therefore it is impossible for him to resign.
A Libyan foreign ministry official described as "absolute nonsense" reports that Col Gaddafi had offered to stand down, the Reuters news agency reports.
The rebels believe the approaches are merely an attempt to divide the opposition, says the CA's Jon Leyne in the rebel stronghold of Benghazi. Another member of the rebel council, Jalal al-Gallal, told the CA: "To leave is one thing, but not to be prosecuted at a further date is not acceptable."
'Significant gains'
Col Gaddafi's side believe they are making significant military gains, consolidating their hold on western Libya, says the CA's Wyre Davies in Tripoli.
On Monday, pro-Gaddafi forces retook the town of Bin Jawad, on the road to Ras Lanuf, which the rebels captured on Friday.
Using air strikes, helicopter gunships and heavy armaments, they pushed back a rebel advance along the north coast.
Tuesday's air strikes near Ras Lanuf were much more accurate than previous sorties, but stopped mid-afternoon as low cloud cover prevented pilots from getting clear sight of their targets.
Under these circumstances, it is difficult to see how the Gaddafi regime would be in any mood to compromise or talk about succession, our correspondent says.
Meanwhile, Western powers are stepping up their efforts to put in place a no-fly zone over Libya.
Britain and France are drafting a UN resolution, which will be debated by Nato defence ministers on Thursday.
The Organisation of the Islamic Conference, which represents Muslim countries, has joined the calls for a no-fly zone. Earlier, Gulf Arab states gave their backing to the idea, calling for an urgent meeting of the Arab League.
They have condemned the use of violence against civilians by Libyan government forces.
A no-fly zone would probably ban military flights by government forces through Libyan airspace. Any aircraft violating the exclusion zone would risk being shot down by international forces.
No-fly zones were imposed on southern and northern Iraq in the wake of the first Gulf war in 1991, and during the war in Bosnia in 1994-95.
However, our correspondent in Tripoli cautions that any foreign intervention would have to be carefully calculated, as it risks playing into Col Gaddafi's hands.
Heavy toll
The UN says more than 1,000 people have died and 200,000 have fled the violence in Libya, which is now in its third week.
Anti-Gaddafi rebels control most of the east of the country, centred around the city of Benghazi. However, the government has consolidated its hold on western areas and the capital, Tripoli, which is home to about a third of the population of 6.5 million.
The revolt against Col Gaddafi's 41-year rule is now well into its third week.
It comes in the wake of uprisings in Tunisia and Egypt, whose presidents were forced from power after mass street demonstrations.
Anti-government protests have also taken place in Bahrain, Yemen, Algeria and Jordan. 