Abuja - The Nigerian air force is flying over The Gambia, an official said on Thursday, as African troops seemed ready to force incumbent Yahya Jammeh to quit after his December election defeat.President-elect Adama Barrow was sworn in at the country's embassy in Senegal, while Jammeh has continued to cling on to power.Jammeh initially acknowledged president-elect Adama Barrow as the victor in the December vote but later rejected the result. "I confirm that the armed reconnaissance air force are over Gambia," Nigerian Air Force spokesperson Ayodele Famuyiwa told AFP. "They have the capacity to strike." Famuyiwa said that negotiations were still ongoing with Jammeh, a leader who has ruled the West African country for 22 years. "What we understand right now is that it appears he's trying to reconsider his position, he may stand down," Famuyiwa said, speaking from Abuja. "But we have our troops there and they are there to enforce the mandate."The UN Security Council was set to vote on Thursday on backing Ecowas efforts to force Jammeh to hand over power as the West African regional bloc amassed a military force ready to intervene.The Economic Community Of West African States has repeatedly called on Jammeh to accept his defeat and honour the country's constitution.