Peace talks to resolve the Centrafrican rebel crisis were suspended until Thursday, with no settlement in sight after the rebels demanded that President Francois Bozize resign and be brought before the International Criminal Court for war crimes.

"There is no alternative, only Bozize's resignation," said Florian Ndjadder, a spokesman for Seleka -- an umbrella group of several rebel factions -- after 12 hours of talks with a government delegation.

"Centrafricans' only problem is Bozize, that's it," he added.

Representatives of Seleka, which launched a major offensive last month and has stormed to within striking distance of the capital, left the meeting at midnight but were expected back at the bargaining table Thursday morning.

"Tonight it's deadlock but the rebels will be back on Thursday," said an official at the Gabonese foreign ministry.

Seleka earlier demanded in a memo distributed at the first day of the talks "that proceedings be taken against Francois Bozize at the ICC".

It accused the Central African head of state of "war crimes and crimes against humanity" including "detentions and false imprisonment, kidnappings, disappearances, assassinations and summary executions".

The three-way talks between the Central African government, rebels and the political opposition are being brokered by regional bloc the Economic Community of Central African States (ECCAS) in the Gabonese capital Libreville with the backing of the United Nations and the United States.

The talks were to focus on renegotiating peace agreements signed by Bangui between 2007 and 2011 which rebels say have been violated.

Seleka launched an offensive in the north on December 10 and soon crossed most of the Central African Republic, an impoverished country of five million people roughly the size of former colonial master France.

Capturing several key towns along the way, the rebels moved southward towards Bangui, but stopped around 160 kilometres (100 miles) from the capital after regional powers sent troops to bolster the embattled army.

On Wednesday, the head of Chad's military contingent in the country said he had met with rebels around 10 kilometres (six miles) north of Damara, the last major town between Seleka and the capital, and asked them to retreat.

Bozize, who took power in a 2003 coup, has warned he would not leave his job.

The chair of the peace talks, Congolese Foreign Minister Basile Ikouebe, urged Bozize's foes as the opening session got under way to "stick to African Union rules on regime change".

The rebels demanded recognition by Bozize and his regime "of their military defeat and abdication in the interest of the people of Central Africa". They further asked Bozize to "find himself a safe haven".

ECCAS foreign ministers on Tuesday said they "regretted that all parties continue to make incendiary statements" and warned of "the complexity of the task" ahead of them.

Bozize -- who is not expected to attend the talks in person -- lashed out at the rebels on Tuesday night, branding them "terrorist mercenaries".

Voted back into office twice, in 2005 and 2011, he has been accused of plotting to modify the constitution to allow him to seek a third term in 2016.

But the government delegation had voiced confidence that concessions Bozize has offered so far -- he has proposed a national unity government and said he would not try to seek an unconstitutional third term -- would go a long way toward resolving the conflict.

Wednesday's talks are to be followed on Thursday by a summit of ECCAS heads of state, in which Bozize is expected to take part.

ECCAS on Tuesday urged the government to back a "regional approach" to the crisis, an implicit criticism of the troop reinforcements sent by South Africa -- not part of the regional bloc -- to shore up Bozize's position in Bangui.

The rebel offensive has raised international alarm of a prolonged conflict engulfing the mineral-rich, impoverished country known for coups and mutinies.

In France, the foreign ministry welcomed the launch of talks.

"Negotiation is more necessary than ever. We call on all parties to find the path to a durable political solution to the crisis," said ministry spokesman Philippe Lalliot.