The United Nations is likely to vote next month on a peacekeeping force for Mali, French Foreign Minister Laurent Fabius said Tuesday.

"We will move from the current framework... to a new diplomatic set-up, a peacekeeping operation which would probably be voted in April and implemented two months later," he told the National Assembly's foreign affairs committee.

One of the armed Islamist groups occupying northern Mali, Ansar Dine, said Thursday it was revoking a pledge to end hostilities made last month during peace negotiations in Algeria.

"Ansar Dine (Defenders of the Faith) has decided to revoke the offer to stop hostilities together with the negotiations being conducted in Ouagadougou," said Ansar Dine's leader, Iyad Ag Ghaly, in a statement published by Mauritanian news agency Sahara Medias.

U.N. Secretary General Ban Ki-moon urged late Saturday quick implementation of a West African accord requiring a military junta in Mali to step down and hand over power to lawful authorities.

The junior officers who seized power in Mali last month have agreed with West African bloc ECOWAS to give up power in return for an amnesty deal and a lifting of sanctions that the regional body had imposed on landlocked Mali.