The leader of Zaire’s rebels agreed Saturday to enter negotiations to halt his offensive on the government, a mediator said. But it appeared unlikely any such talks would come soon enough to stop an assault on this strategic city.

Dutch Development Minister Jan Pronk met rebel leader Laurent Kabila in the eastern city of Goma on Saturday and said he had agreed for the first time to accept a U.N. plan for a cease-fire.

Kabila’s adviser on foreign affairs, Bizima Karha, announced after the meeting that the rebels also would allow aid and relief organizations access to more than 100,000 refugees caught in the fighting in eastern Zaire, Pronk said.

The Dutch minister said U.N. Secretary-General Kofi Annan had asked him to urge Kabila to accept a U.N. peace plan, which calls for an immediate cease-fire.

But with rebel fighters poised to launch a battle for control of Kisangani, it appeared unlikely an accord would be negotiated beforehand.

Kisangani, on the Zaire River, is one of the largest cities in the central African country and has an international airport, which has served as the army’s headquarters.

Rebel spokesman Nyembwe Kazadi, who spoke earlier by phone from Dar es Salaam, Tanzania, said rebel troops already at the northern approaches to Kisangani were awaiting the arrival of columns advancing from the south and the east.

Map of area.