By Ange Aboa

BANGUI (Reuters) - Central African Republic President Francois Bozize will refuse to leave power during talks with rebels, his spokesman said on Thursday, rejecting the insurgents' main demand and raising the prospect of a return to fighting.

The Seleka rebel alliance, which has accused Bozize of reneging on a past peace deal, advanced to within striking distance of the mineral-rich nation's capital this week before bowing to international pressure to start negotiations.

A week before those talks were due to start, a spokesman for Bozize's ruling KNK party said the president's departure would not be on the agenda.

"The question of President Bozize leaving ... will be rejected systematically if it is proposed," Cyriac Gonda told Reuters.

"For us, the solution is to form a unity government with everyone," he added, reiterating a previous offer by Bozize to give government posts to the rebels.

The spokesman for the CPSK, one of the rebel groups that form Seleka, said on Thursday a peace deal would not be possible without Bozize's unconditional exit.

The advance by Seleka, an alliance of five armed groups, was the latest in a series of revolts in a country at the heart of one of Africa's most turbulent regions.

CAR remains plagued by poverty and underdevelopment despite its reserves of diamonds, gold and other minerals.

French nuclear energy group Areva mines the country's Bakouma uranium deposit - France's biggest commercial interest in its former colony.

REGIONAL SUPPORT

Seleka fighters have swept aside regionally-backed government defenses to within 75 km (45 miles) of Bangui since launching their assault on December 10.

African leaders are organizing peace negotiations in Gabon's capital Libreville that are expected to take place on January 10. The United States, France and the European Union have urged both sides to reach a political solution and spare civilians.

Martin Ziguele, a former prime minister and now a leading opposition figure in CAR, said on Thursday Bozize's departure should be considered during the Libreville talks. Continued...