The Gambia's defeated President Yahya Jammeh has asked for a deadline for him to leave office or be forced out by UN-backed forces to be extended until 16:00 GMT on Friday.
By land, sea and air, Gambia is surrounded. A total of 7,000 men will participate in the mission to re-establish democracy in Gambia
The earlier deadline of noon passed as the Guinean and Mauritanian presidents arrived in Banjul for last-ditch talks.
Mr Jammeh's elected successor, Adama Barrow, was sworn in as president at a ceremony in Senegal on Thursday.
Troops acting in support of President Barrow have paused their advance.
The forces from the Economic Community of West African States (Ecowas) regional grouping are backed by the United Nations.
They crossed into The Gambia from Senegal on Thursday but have been told not to advance further until the talks have finished.
Mr Barrow's legitimacy as president has been recognised internationally, after he won last month's elections.
Mr Jammeh remains at the state house in The Gambia's capital, where soldiers are calm, the BBC's Maxime Le Hegarat reports.
Mr Jammeh's term expired at midnight on Wednesday - but, while still president, he engineered a parliamentary vote to extend his presidency. As Mr Barrow has already been sworn in, the country could be said to have two presidents.
Guinea's President Alpha Conde and Mauritanian President Mohamed Ould Abdel Aziz arrived in Banjul on Friday morning for the talks with Mr Jammeh.
The chairman of the Ecowas commission, Marcel Alain de Souza, said that if the meeting with Mr Conde proved unsuccessful, military action would follow.
The presidents of Guinea and Mauritania have come to give Yahya Jammeh a final chance of a managed exit.
Mr Jammeh can walk out of the State House and leave the country peacefully, or West African troops will enter the capital to remove him from power.
The streets of Banjul are still empty; shops and markets are still closed. There's an anxious wait here though people feel the end of this political crisis is near.
It now seems clear that the Gambian security forces will not defend Mr Jammeh, leaving him no other prospect than to end his 22-year rule.
Regional powers are sending a strong message across the continent, that they stand ready to fight for democracy.
Ecowas said that its forces had encountered no resistance after entering The Gambia.
The troops are from Senegal and other West African countries.
Mr Barrow, who remains in Senegal, has said that he will not return to Gambia's capital, Banjul, until the military operation has ended.
The threat by the West African regional bloc Ecowas to remove Mr Jammeh by force is supported by the 15-member UN Security Council, although the council has stressed that a political solution should be the priority.
A Senegalese army spokesman, Col Abdou Ndiaye, told the BBC that troops who were now in The Gambia were prepared to fight if necessary.
"It is already war, if we find any resistance, we will fight it," he said, adding: "If there are people who are fighting for the former president, we will fight them."
But Col Ndiaye said the main goal of Ecowas was to restore democracy and to allow the newly-elected president to take power.
Tourists have been evacuated from The Gambia and the UK's Foreign Office has advised against all but essential travel to the West African country.