The Gambia’s President-elect Adama Barrow has tweeted that he is to be sworn in as president in The Gambian embassy in the Senegalese capital Dakar at 16:00 local time (16:00 GMT).
Earlier reports had suggested he would be inaugurated at a location in The Gambia.
It follows the failure of last-ditch negotiations to persuade defeated President Yahya Jammeh to step down.
A deadline has now passed without Mr Jammeh leaving power.
West African military forces are poised to move in to enforce the transfer of power.
Unconfirmed reports say troops from Senegal have already crossed the border to secure a number of towns, with the help of Gambian soldiers.
Mr Jammeh – who has been in power for more than two decades – disputes the election result.
Gambia’s army chief, previously seen as a close ally of Yahya Jammeh, has been quoted as saying he would not risk his men’s lives for a political dispute.
The NGO Save the Children has warned of a possible humanitarian emergency on both sides of the border between The Gambia and Senegal if the political crisis in The Gambia results in an outbreak of violence.
It quotes the UN as saying that up to 50,000 people, mostly women and children, have already left urban centres in The Gambia, with about half heading to villages in other parts of the country and half crossing the border into Senegal.
Save the Children’s Bonzi Mathurin said public services could be overwhelmed:
“Migration between Gambia and Senegal has been relatively fluid because often people have family members on both sides of the boarder.
However, any sudden mass movement of people would simply overwhelm public services which are already struggling and raise the possibility of humanitarian”
Health facilities in The Gambia were still operating but the majority of foreign doctors had left the country, Save the Children said.
Many schools remain closed and some that are open were advising parents to keep their children at home, it said.
Gambia’s army chief, previously seen as a close ally of Yahya Jammeh, has been quoted as saying he would not risk his men’s lives for a political dispute.
But Mr Jammeh is a military man and some of his generals may try to fight, even though they would be vastly outnumbered by the Senegalese and Nigerian forces. The Gambia’s armed forces number is just 2,500.
One key question is how ordinary Gambians see the Senegalese troops if they do cross the border. The Gambia and Senegal are made up of the same ethnic groups which were divided by colonial borders, so they speak the same languages and share the same culture.
However, a fierce rivalry has developed between the two nations, with many Gambians feeling they are looked down on by their more numerous, French-speaking neighbours.
So while supporters of Adama Barrow will presumably see any intervention favourably, there is also a danger that it could be seen as a foreign invasion force.
Many Senegalese have long accused Mr Jammeh of backing a separatist rebel group in its southern region of Casamance, which Senegal’s army has never been able to defeat militarily, so there is also a possibility of Mr Jammeh supporters adopting rebel tactics.
Reports indicate that Gambia`s Embassy is shut in Senegal’s capital Dakar with no guards or staff.
The embassy is due to host the controversial inauguration of property developer Adama Barrow as the third president of The Gambia later today.
