Political veteran Joseph Boakai was on Friday close to victory in Liberia's presidential race against incumbent George Weah.
Former vice president Boakai had garnered 50.89 percent of votes cast, with Weah on 49.11 percent with more than 99.5 percent of the polling stations tallied following Tuesday's second-round poll, said electoral commission head Davidetta Browne Lansanah.
The results have been frozen at a large proportion of the 25 remaining polling stations, due to an abnormal turnout or a number of votes exceeding the number of registered voters, she said.
Political expert Abdullah Kiatamba said it looked certain that former football great Weah could not make up the gap.
"The reality at this moment is that, given the numbers, it is literally impossible to reverse the gain," he told AFP.
"To do so it means the CDC (Weah's party) will need to win numbers that are four or five times the current trend."
Thomas Kaydor, a political sciences lecturer at the University of Liberia, agreed.
"Even if you add up all the votes from the 25 remaining polling stations, George Weah cannot win," he said.
According to Friday's figure, Boakai was 28,000 votes ahead of Weah.
Just over 1.6 million ballots have been counted. Around 2.4 million Liberians were eligible to vote on Tuesday, but no turnout figures have been released.
Dozens of Boakai's supporters danced in celebration outside one of his party's offices in the capital Monrovia.
- 'Largely' peaceful -
The election winner will lead the English-speaking country of around five million people, one of the poorest in the world, for six years.
The elections were the first since the United Nations in 2018 ended its peacekeeping mission, created after more than 250,000 people died in two civil wars in Liberia between 1989 and 2003.
ECOWAS, the Economic Community of West African States, also congratulated all stakeholders for the "largely" peaceful election.
But it noted isolated incidents that led to "injuries and hospitalisations" in the provinces of Lofa, Nimba, Bong and Montserrado.
The two observation missions called on the candidates and their supporters to show restraint and to wait patiently for the final results.
Clashes during the election campaign left several dead before the first round and raised fears of post-election violence.
Boakai is an old political hand, having served as vice president to Ellen Johnson Sirleaf, Africa's first elected female head of state, from 2006 to 2018.
He has also held a multitude of positions within the state and in the private sector.
At 78, he is significantly older than Weah, 57, who remains popular among younger voters but has had to defend a criticised record in power.
Victory would be sweet revenge for Boakai, who lost to Weah by a large margin in the second-round presidential vote in 2017.
- Accusations of corruption -
Weah's election six years ago had sparked high hopes of change in Liberia, which is still reeling from civil war and the 2014-2016 Ebola epidemic.
But critics have accused his government of corruption and him of failing to keep a promise to improve the lives of the poorest.
This week's run-off vote was always going to be closer, after the two men finished neck-and-neck in the first round, with a national lead of just 7,126 votes for Weah.
Boakai has promised to develop infrastructure, attract investors and tourists, and improve the living conditions of the poor.
More than a fifth of the population lives on less than $2.15 a day, according to the World Bank.
Boakai has forged alliances with local barons, including former warlord and senator Prince Johnson, who supported Weah six years ago.