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.
A BBC correspondent in the capital, Banjul, says it is eerily quiet and everything has come to a standstill; people are staying indoors:
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.
Meanwhile, the lawyer for Gambian strongman Yahya Jammeh has fled to Senegal after writing a letter to the defeated president urging hi to give up power, Nigeria’s Premium Times newspaper reports.
Edu Gomez said he had worked for M Jammeh under “tremendous pressure and coercion”, it reports.
The newspaper also quotes the letter as saying: On Tuesday 17th January 2017, my son and I took a crucial decision to seek sanctuary in the sister Republic of Senegal. This was found necessary due to the mounting fear and rapidly increasing tension at every passing moment.”
The BBC has not obtained independent confirmation of the report.
Mr Gomez represented Mr Jammeh in his legal bid to annul his defeat at the hands of property developer Adama Barrow in the 1 December election.
