West African leaders are still pursuing mediation to ensure a peaceful transfer of power in The Gambia where President Yahya Jammeh refused to accept defeat in an election last month.

Liberia's president, Ellen Johnson Sirleaf, told reporters on Saturday, after a meeting among regional leaders in Ghana's capital, Accra, that regional bloc ECOWAS did not yet intend to deploy its standby military force in the country.

"We are committed to a peaceful mediation and a peaceful transfer of power in The Gambia. We will continue to pursue that for now," said Sirleaf, who chairs the 15-member body.

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Asked if the regional group would deploy a standby force soon, she said "no", adding that ECOWAS was closely monitoring proceedings in The Gambia's Supreme Court, where Jammeh is challenging the poll result.

Nigerian foreign minister Geoffrey Onyeama said ECOWAS would hold a meeting on Monday in Abuja to discuss further steps.

"There are some disturbing information the [Nigerian] president [Muhammadu Buhari] is hearing which he needs to verify and the Abuja meeting will take a final decision," he said, without elaborating.

Buhari has been appointed by ECOWAS as a mediator.

Jammeh, a former coup leader who has ruled the country for 22 years, initially accepted his defeat by opposition figure Adama Barrow in the December 1 election. But a week later, he reversed his position, vowing to hang onto power despite a wave of regional and international condemnation.

Diplomats are concerned the impasse over the poll could escalate quickly into violence.