Jammeh, who had been in power for 21 years, lost the December 1 presidential election to opposition leader, Adama Barrow.
He initially accepted the election results but reversed himself a week after, claiming that new evidence indicated the polls were rigged.
He has since vowed not to leave office on January 19 when his mandate expires. But the Economic Community of West African States (ECOWAS) condemned the move and warned that he may be forced out of office.
On December 17, during the ECOWAS Summit in Abuja, President Buhari was designated as the Mediator for The Gambia with Mr. John Mahama, the out- going President of Ghana as Co-Mediator.
On Saturday, the presidency in Nigeria said Mr. Buhari had activated the process for a smooth transition.
“In the discharge of his mandate as the Economic Community of West African States (ECOWAS) mediator for The Gambia, President Muhammadu Buhari has activated the process for the execution of his task,” said Buhari’s spokesman Garba Shehu.
The Summit had given the terms of reference to include ensuring the safety of the President-Elect, Adama Barrow, the political leaders and the entire population; upholding the result of the Presidential election held on December 1, 2016 and ensuring that the President-elect is sworn into office on January 19, 2017, in conformity with the constitution of the country.
“On the direction of the President, the Minister of Foreign Affairs, Geoffrey Onyeama is leading a Mediation Support Team (MST), working with the team of the Co-Mediator, President Mahama. The committee has begun immediate consultations with leaders in the sub-region as well as with international partners,” Shehu said.