"This crisis has not been solved by these talks," said spokesman Halifa Sallah, adding that more efforts are needed to narrow differences.
Sallah spoke after Nigeria's president led talks Friday with Gambia's President Yahya Jammeh and President-elect Adama Barrow in Gambia as part of mediation efforts led by the West African regional bloc ECOWAS.
"The expectation is that the Gambian people and the international community will not sit and wait and preside over a country that is destroyed by war — destroyed in terms of property, destroyed by human beings and human beings suffering," Sallah said, stressing that Gambia's constitution clearly spells out what is to happen on the day a president's term expires. "The person declared elected should take and assume office."
Meanwhile, the African Union announced it will cease to recognize President Jammeh as Gambia's legitimate leader as of Jan. 19, when his mandate expires. The decision by the AU's Peace and Security Council warns Jammeh of serious consequences if his actions lead to the "loss of innocent lives" and calls on Gambia's security forces to exercise restraint.
Mohamed Ibn Chambas, the U.N. special representative for West Africa and the Sahel, told the U.N. Security Council Friday that the Nigerian-led delegation was "to leave no doubt about the determination of ECOWAS to use all necessary means, including force to have the will of the Gambian people upheld."
If this is deemed necessary, Chambas said, ECOWAS intends to seek the endorsement of the AU Peace and Security Council and the Security Council to deploy troops to Gambia.
The political uncertainty has in the past 10 days sent several thousand people, mostly children in buses accompanied by women, fleeing across border to Senegal where they are likely staying with relatives or host families, the United Nations Refugee Agency said Friday.
As the international community looks for a peaceful way out of the crisis, Nigerian President Muhammadu Buhari had been authorized to offer Jammeh asylum, if necessary, during Friday's visit.
A definitive plan by ECOWAS will be made after Buhari and Liberian President Ellen Johnson Sirleaf continue discussions with other leaders, and with Barrow in Bamako, Mali, where a France-
But the West African regional bloc also has a military force on standby to intervene if Jammeh does not step down.
Jammeh at first accepted his Dec. 1 election loss, even making a telephone call to concede on national television, but then changed his mind and declared that "only Allah" can deny him victory. His party is now contesting the results in court.
President-elect Barrow is renewing his offer to Jammeh for direct discussions on the crisis, telling the BBC that "I'll be very willing to talk to him directly."
The ruling party's court challenge to the election results shows complications. Gambia's Supreme Court, short of judges, has said it might not be able to consider the challenge until May, and Jammeh says Gambia should await its decision.
Jammeh took power in a coup in 1994 and is accused of gross rights violations including arbitrary detentions, torture and the killings of opponents in this tiny country of 1.9 million people that is nearly surrounded by Senegal.
Jammeh might be wary of a Nigerian promise of safe haven. Nigeria offered asylum to Liberian warlord Charles Taylor in 2003 to help end the civil war he started in 1989, but it was forced by international pressure to hand Taylor over in 2006 for trial for war crimes committed in Sierra Leone. Taylor was convicted in 2013 and is serving a 50-year sentence in a British prison.
AP writers Michelle Faul in Lagos, Nigeria, and Edith M. Lederer at the United Nations contributed.