Senegal will lead a military intervention to oust Gambia's outgoing President Yahya Jammeh if he refuses to step down when his mandate expires on 19 January, the Economic Community Of West African States (Ecowas) has claimed. Jammeh has claimed he will not step down despite the fact he lost the presidential election held on 1 December.

Adama Barrow, head of a coalition of opposition parties and member of the United Democratic Party (UDP), emerged as winner of the vote.

Jammeh, who took power in a bloodless coup in 1994, originally conceded defeat. He now intends to contest the vote at the Supreme Court due to what he says are "unacceptable abnormalities".

The country's apex court adjourned the case to 10 January.

Marcel Alain de Souza, chairman of the Ecowas commission, told BBC Afrique that although Ecowas wished to resolve the issue peacefully, "stand-by forces" were on alert and would be deployed "to restore the people's wish".

Barrow is due to be sworn in on 19 January. The President-elect, who previously worked in an Argos store in north London, told IBTimes UK he considers himself the "rightful leader" of the country and will go ahead with the inauguration in spite of Jammeh's efforts to cling on to power.

Jammeh's U-turn 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%.

Jammeh, whose decision to challenge the election result sent shock waves across the region, said he will resist pressure to step down, criticising leaders from neighbouring countries for urging him to concede.

Earlier in December, four West African leaders – from Nigeria, Liberia, Sierra Leone and Ghana – met Jammeh and urged him to accept defeat. The leaders left without managing to secure a deal.

Macky Sall, President of Senegal, which entirely engulfs Gambia, was not part of the delegation. The two countries have a history of poor relations.

On 14 December, security forces initially pledging alliance to Barrow backtracked claiming they were loyal to Jammeh before taking over the electoral commission headquarters. The move sparked fears of possible violence.