BANJUL, Gambia (AP) — The leaders of Guinea and Mauritania arrived Friday in Gambia's capital in a last-ditch diplomatic effort to get defeated President Yahya Jammeh to cede power, while a regional military force awaited orders to force out the longtime leader.

The regional leaders had set a deadline of noon (7 a.m. EST) for Jammeh to step aside, but it passed as the Guinean and Mauritanian leaders arrived.

Adama Barrow, who was elected president last month, was sworn in Thursday, and the U.N. Security Council voted unanimously to approve the regional military intervention. The inauguration took place at the Gambian Embassy in neighboring Senegal for Barrow's safety.

The West African regional force, including tanks, moved in during the evening without facing any resistance, said Marcel Alain de Souza, chairman of the West African regional bloc, ECOWAS. At least 20 military vehicles were seen Friday at the border town of Karang.

The regional force included troops from Senegal, Ghana, Nigeria, Togo and Mali, and they moved in after Barrow's inauguration and the U.N. vote.

An increasingly isolated Jammeh remained in the official residence, State House, in Banjul. He dissolved his Cabinet on Thursday, said Malick Jones, the director of national television. Several ministers have resigned in recent days and some have fled the country.

Guinean President Alpha Conde arrived in Banjul with Mauritanian President Mohamed Ould Abdel Aziz. Mauritania has been mentioned as a possible home in exile for Jammeh.

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

Jammeh "has the choice of going with President Alpha Conde," he said, but if that fails, "we will bring him by force or by will."

"Our troops will advance on Banjul, de Souza said. "Until the last minute, we still think there is a solution resulting from a dialogue."

Jammeh began negotiations Thursday with ECOWAS and agreed to step down, but demanded amnesty for any crimes he may have committed during his 22 years in power and wanted to stay in Gambia, in his home village of Kanilai, de Souza said. Those demands are not acceptable to ECOWAS, he added.

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

At a news conference in Nouakchott before leaving for Gambia, Abdel Aziz said he would "never understand" why Jammeh backed off from his initial pledge to accept defeat and step down, Mauritanian state media reported.

In his inaugural speech, which took place under heavy security, Barrow urged Jammeh to respect the will of the people and step aside. He also called for Gambia's armed forces to stay in their barracks.

Some of Gambia's diplomatic missions have begun switching their allegiance.

"We embrace and support the new president Adama Barrow," said Almamy Kassama, an official at the Gambian mission to the African Union in Addis Ababa, Ethiopia, in an email.

The U.S. supported the regional force's intervention and was in touch with officials in Senegal, said State Department spokesman John Kirby, adding that he didn't have tactical information, but "obviously, it's very, very tense."

It is uncertain if Gambia's army will try 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 he was not authorized to talk to reporters.

Senegalese radio station RFM reported 30 Gambian soldiers had crossed into Senegal to fight alongside the regional forces.

"I think the Gambian military would know it's outnumbered," said Maggie Dwyer, an expert on West African armed forces at the University of Edinburgh. "Gambia's military has very little combat experience. This would be a very difficult situation for them."

She estimated it had 2,400 troops at most, plus fewer than 1,000 paramilitary forces.

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

She pointed to an online video that appeared to show army chief of staff Ousman Badgie celebrating Barrow's inauguration as "a pretty clear indication of his stance."

Barrow, as commander in chief, requested the support of military leaders, said Halifa Sallah, spokesman for the coalition supporting the new president. "People are confident that change will be affected and there will be a peaceful resolution," he said.

Soldiers at checkpoints in Banjul appeared relaxed, with one telling visitors, "Welcome to the smiling coast."

Other nations have begun stepping away from Jammeh, with the African Union saying the continental body no longer recognizes him.

About 45,000 people have fled Gambia for Senegal, fearing violence, according to the Senegalese government and the U.N. refugee agency. About two-thirds are children accompanied by women, the U.N. said.

Only about a few thousand international tourists are believed to still be in Gambia, and efforts continued to evacuate them.

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Dione reported from Dakar, Senegal. Elias Meseret in Addis Ababa, Ethiopia, contributed.