BANJUL, Gambia (AP) —  Gambia's defeated President Yahya Jammeh must cede power by noon Friday or he will be dislodged by a regional force that has already moved into the country, West African officials said.

If Jammeh refuses to leave Gambia by midday (12:00GMT) the regional troops will force him out, said Marcel Alain de Souza, chairman of the West African regional bloc, ECOWAS.

The West African regional force including tanks moved into Gambia Thursday evening and has met no resistance, said de Souza. At least 20 military vehicles were seen at the border town of Karang on Friday morning. They were not traveling but appeared to be waiting for further instructions.

The regional force, including troops from Senegal, Ghana, Nigeria, Togo and Mali, charged into Gambia after the inauguration of Adama Barrow as the country's new president and the U.N. Security Council voted to approve the regional military intervention.

Barrow, who won Gambia's presidential election in December, was sworn into office at the Gambian embassy in neighboring Senegal, where he is for his safety.

Senegalese military spokesman Col. Abdoul Ndiaye confirmed Friday that the regional force would give Jammeh until midday to step down but then would resume their mandate to force him from power. Jammeh remained in the official residence, State House, in Gambia's capital, Banjul.

Jammeh dissolved his Cabinet on Thursday, said Malick Jones, the director of national television. Several of his ministers had already resigned in recent days, in some cases fleeing the country.

Guinean President Alpha Conde was flying to Banjul to negotiate with Jammeh after first going to Mauritania, said de Souza. Mauritania has been mentioned as a possible country where Jammeh could go into exile.

The leaders of Guinea and Mauritania were expected to arrive in Banjul within the hour, said U.N. special representative for West Africa and the Sahel, Mohamed Ibn Chambas.

Conde will offer Jammeh the chance to step down peacefully, said de Souza.

Jammeh "has the choice of going with President Alpha Conde," said de Souza. "If, at 12 o'clock, he does not make up his mind, we will bring him by force or by will. Our troops will advance on Banjul. Until the last minute, we still think there is a solution resulting from a dialogue."

Jammeh started negotiations with ECOWAS on Thursday and agreed to step down but demanded an amnesty for any crimes that he may have committed during his 22 years in power and that he be permitted to stay in Gambia, at his home village of Kanilai, said de Souza.

Those demands are not acceptable to ECOWAS, said de Souza.

Jammeh's continued presence in Gambia would "create disturbances to public order and terrorist movements," said de Souza. ECOWAS wants newly inaugurated president Barrow to take power in Gambia without any security threats, said de Souza.

Barrow, in his inaugural speech, which took place under heavy security, called on Jammeh to respect the will of the people and step aside. The new president also called on Gambia's armed forces to remain in their barracks as the regional military intervention got underway.

Shortly after the inauguration, the U.N. Security Council unanimously approved a resolution expressing "full support" to Barrow, calling on Jammeh to step down and condemning his attempts to usurp power. The resolution also backed the regional efforts to get Jammeh to respect the election results.

The United States supports diplomatically the regional force's intervention and is in touch with officials in Senegal, State Department spokesman John Kirby told reporters. He said he didn't have tactical information but "obviously, it's very, very tense."

It is not certain that Gambia's army, estimated to be smaller than 2,000 troops, will fight to keep Jammeh in power. A soldier with close knowledge of the situation said three barracks had indicated they would support Barrow. The soldier spoke on condition of anonymity because they were not authorized to speak to reporters.

"I think the Gambian military would know it's outnumbered," said Maggie Dwyer, an expert on West African militaries at the University of Edinburgh. "Gambia's military has very little combat experience. This would be a very difficult situation for them." She estimated the military's size at 2,400 at most, plus paramilitary forces of less than 1,000.

"My guess is, a very small number would actually put their life on the line for Jammeh," though some might stand by him in the hope of getting any deal he might get to avoid prosecution, Dwyer said.

"People are confident that change will be affected and there will be a peaceful resolution," said Halifa Sallah, spokesman for the coalition supporting Barrow.

African nations began stepping away from Jammeh, with Botswana announcing it no longer recognized him as Gambia's president. The African Union earlier announced that the continental body would no longer recognize Jammeh once his mandate expired.

About 45,000 people have fled Gambia to Senegal, fearing an outbreak of violence, according to the Senegalese government and the U.N. refugee agency. About 75 percent of those refugees are children accompanied by women, the U.N. said.

It is estimated that a few thousand international tourists are still in Gambia and efforts continue to evacuate them from the country.

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Dione reported from Dakar, Senegal