Several people were killed during post-poll opposition protests
Opposition parties in Gabon have rejected the terms of a re-count of votes from last month's controversial presidential poll.
Activists, who alleged widespread vote rigging, were angered after a court ruled that opposition observers would not be allowed to oversee the re-count.
One beaten candidate said the re-count would now have "no value".
Ali Ben Bongo, son of Gabon's long-time leader Omar Bongo, was declared winner of the August election.
But his opponents immediately cried foul, sparking violent protests in which several people were killed.
Opposition activists forced the re-count alleging vote rigging.
They wanted their representatives to oversee the process, but the Constitutional Court disagreed.
The re-count was delayed for a day while officials met opposition leaders, but the court now says it will begin to re-count the votes at 2100 local time (2000 GMT).
Constitutional Court President Marie Madeleine Mborantsuo said bailiffs would act as both officers of the court and representatives of the candidates.
AFP news agency quoted her as saying the court was "not a political organ where political figures can come and impose their point of view".
Beaten candidates in the election say they do not approve of the court's move.
"This recount has no value for us, nor for the truth that we are looking for," said Andre Mba Obame, who finished second in the election.
Earlier a senior official of the ruling Gabonese Democratic Party (PDG), which backed Mr Bongo, said he was not worried.
"The election took place openly. Whether you re-count once or 100 times, it doesn't change the results," said PDG Secretary General Faustin Boukoubi.
Gabon is sub-Saharan Africa's fourth biggest oil producer and Africa's second biggest wood exporter, although most of its 1.4 million people live in poverty.
Last month's election was called after the death of Omar Bongo, one of the world's richest men, who had ruled the nation for four decades.