Libya's rebel leader said on Wednesday that his council had offered to allow Muammar Gaddafi to stay in the country provided he step down first, but that this offer had now expired.

"This offer is no longer valid," Mustafa Abdel Jalil told reporters in the rebel-held eastern city of Benghazi.

Abdel Jalil said the offer was made about a month ago through U.N. envoy Abdel Elah al-Khatib, with a two-week deadline attached. The two weeks had passed and the offer was no longer valid, he said.

Khatib visited both Benghazi and Gaddafi's stronghold of Tripoli this week to seek a negotiated end to the war that has dragged on despite four months of NATO air strikes.

Khatib did not give any details on his initiative, but a diplomat said it involved declaring a ceasefire and creating a power-sharing government that would not include Gaddafi.

Asked about the idea of a power-sharing government, Abdel Jalil said it was "laughable" but gave not details.

A rebel source said Khatib had suggested a five-member power-sharing council including two Gaddafi loyalists and two rebels. However, he had no suggestion about who might chair the council or lead the country.

The source said the plan would have led to a worsening of the civil war and that the rebels now believed only the military option remained open to them to end Gaddafi's 41-year rule.