Togo's acting president called for calm on the eve of a presidential poll aimed at ending weeks of political crisis.
Violent protests have been held in the capital Lome
In a televised address, Abass Bonfoh said Sunday's vote was needed to avoid a political vacuum, adding all measures had been taken to ensure security.
Meanwhile, one of the three challengers has withdrawn from the race.
Nicolas Lawson said he could not continue after a minister was sacked for urging a delay to elections saying that they could spark civil war.
Mr Lawson said the Interior Minister Francois Boko had "noted enough irregularities to no longer wish to pursue" the voting process.
"He's fired, replaced and they still want to continue. I'm sorry but I can't go through with this election," Mr Lawson, who was thought to have only a slim chance of winning, told the AFP news agency.
The US also expressed its "deep concern" about the poll after the sacking of Mr Boko.
"The US notes with deep concern allegations by the Togolese Interior Minister that call into question the credibility of this Sunday's presidential election," deputy State Department spokesman Adam Ereli said.
He said the US was concerned because of Togo's history and "persistent reports from within Togo about the prospects for violence and [...] irregularities in voting procedures and tabulations."
The US said the international community would be scrutinising Togo's balloting and vote-counting process.
President Bonfoh, in his address, urged voters "to show moderation so that the vote and the count can take place in the greatest transparency".
The vote was called after an international outcry forced Faure Gnassingbe, installed by the military in February, to step down.
He took power after the death of his father, long-serving President Gnassingbe Eyadema.
Hundreds have taken part in violent political rallies in the capital in the run-up to the election, and at least seven people have been killed.