Mali's military coup leaders must hand over power to a civilian transitional government immediately, the chairman of the West African regional bloc said on Tuesday, as a deadline expired for the ruling junta to appoint interim leaders.

The 15-member Economic Community of West African States (ECOWAS) imposed economic sanctions after the August 18 overthrow of President Ibrahim Boubacar Keita, and said a new president should be appointed by Tuesday.

But the junta pushed through a charter on Saturday that says the interim president can be a soldier or a civilian and has not yet indicated when the new government would be named.

Regional presidents met junta leaders on Tuesday in Ghana in an attempt to quicken the transition.

"Today is supposed to be the day that the junta is to put in place a government, which should respond to the criteria we set out in August. That has not been met," said Ghana President Nana Akufo-Addo, the acting ECOWAS chair, before the start of talks.

Regional leaders fear the coup could set a dangerous precedent in West Africa and undermine a fight in Mali and neighbouring countries in the Sahel region against Islamist militants with links to al Qaeda and Islamic State.

"That country can no longer afford any delay in putting a responsible government in place," he said.

West African leaders have not said what the consequences would be for failing to meet the deadline. The existing sanctions include border closures and the suspension of financial flows.

The charter approved at multi-party talks in Mali also calls for an 18-month transition, while ECOWAS had said that fresh elections should be held within a year.