Senegal has moved troops towards the Gambian border in an effort to force President Yahya Jammeh to accept electoral defeat and step down.
Senegal is leading the operation, which is supported by Nigeria and other states in the region.
Mr Jammeh has been told to leave office by the end of Wednesday and hand over to last month’s election winner, Adama Barrow, who is currently in Senegal. Mr Jammeh has ruled The Gambia since taking power in a coup in 1994.
Wednesday was meant to be his last day in office but parliament granted him three more months in the post.Garba Shehu, official spokesman for Nigerian President Muhammadu Buhari, said Mr Barrow was preparing to be sworn in as president “on Gambian soil” on Thursday.
At least 26,000 Gambians, fearful that violence could erupt, sought refuge in Senegal this week.
Meanwhile, thousands of UK and Dutch tourists are being evacuated from the tiny West African state, which is popular with European holidaymakers because of its beaches.
Why is Senegal taking the lead?
Ecowas, the Economic Community of West African States, mandated Senegal because it almost surrounds The Gambia. Col Abdou Ndiaye, a spokesman for the Senegalese military, said Ecowas had decided on the deadline to try to achieve a diplomatic solution. “Things are getting into place and Ecowas forces are ready to intervene if needed after midnight if we can’t find a diplomatic solution to the Gambian crisis,” he said.
The Ecowas force is seeking UN Security Council endorsement to use “all necessary measures” to help remove Mr Jammeh. The Gambia’s entire armed forces are made up of only about 2,500 troops, making it difficult to see how they can defeat a regional force if it moves in, says BBC Africa Monitoring security correspondent Tomi Oladipo. Nigeria says it sent fighters and other aircraft, along with 200 personnel, to Senegal on Wednesday morning. Nigerian navy vessels are also on standby and a warship that sailed from Lagos on Tuesday will have the task of evacuating Nigerian citizens while putting on a show of force. Ground troops are also being provided by Ghana.