Gambia's outgoing leader Yahya Jammeh has appointed a mediator to help resolve the political impasse with President-elect Adama Barrow. Jammeh, who lost the presidential election held in December 2016, is refusing to step down.

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The leader initially conceded defeat. However, he now intends to contest the election result at the Supreme Court due to what he says are "unacceptable abnormalities".

"I ask everyone to respect the supreme law of our republic and wait for the Supreme Court review and ruling on the election results," Jammeh said during a televised speech on 11 January, according to the BBC.

The apex court said it will only be able to hear Jammeh's petition in May or November, as the "full bench" needed for the case is not available at the moment.

Jammeh, who took power in a bloodless coup in 1994, is expected to step down on 18 January, when his term expires. However, the leader said he would resist pressure to leave office until the court hears his case.

In his speech, Jammeh also criticised the "unprecedented level" of foreign interference in the country's politics.

In December, west African leaders led by Nigeria's President Muhammadu Buhari met Jammeh and urged him to accept defeat. The leaders, who left without managing to secure a deal, are expected to meet Jammeh again in the capital Banjul on 13 January.

President-elect Barrow – head of a coalition of opposition parties and member of the United Democratic Party (UDP) – told IBTimes UK he considered himself the "rightful leader" of the country. He is due to be sworn-in on 19 January.

IBTimes UK interviews president-elect Adama Barrow: I am the rightful leader of this country

Jammeh's U-turn has sent shock waves across in Gambia and across the region, with growing tensions exacerbated by the chief of the army's decision to pledge loyalty to Jammeh instead of Barrow.

Meanwhile Marcel Alain de Souza, the Chairman of the Economic Community Of West African States (Ecowas) has claimed that a military intervention to remove Jammeh was "possible" and that "stand-by forces" – likely led by Senegal – were on alert and would be deployed "to restore the people's wish".

Jammeh's decision followed an admission by Gambia's Independent Electoral Commission (IEC) that it had erred during vote counting, and Barrow's margin of victory had narrowed from 9% to 4%.

Despite the changes, the commission insists that the new tally leaves the outcome of the election unchanged. with Barrow receiving 43.3% of the vote, and Jammeh 39.6%.