Liberian presidential candidate George Weah has called for a re-run of Tuesday's election, saying it was marred by vote-rigging.
George Weah has urged his supporters to remain calm
With almost all the votes counted, his opponent, Ellen Johnson-Sirleaf, has an insurmountable lead.
The former football star has urged supporters to remain calm - although on Friday hundreds staged angry protests in the capital, Monrovia.
The UN Security Council urged Liberians to settle the dispute peacefully.
If Mrs Johnson-Sirleaf's victory is confirmed, she would be the first woman to be elected president anywhere in Africa.
The Weah camp has made allegations of ballot tampering, intimidation and harassment during the vote. An investigation is under way.
International observers say the election was broadly free and fair.
The West African regional group Ecowas has urged the losers to accept the result with dignity and grace.
However, Mr Weah re-iterated his claims of fraud.
"As far as I am concerned there will be a re-run and I am going to pursue that," he told the BBC.
But the candidate said he was telling his supporters to be calm, "because we need to be peaceful".
Despite his appeals, at least one person was injured when UN forces fired tear gas to disperse protesters near the US embassy.
They acted after some of Mr Weah's supporters broke through a line of Liberian riot police trying to hold them back from the embassy, Reuters news agency reports.
The Weah camp is supported by most of the 100,000 ex-combatants from Liberia's 14-year civil war.
Mr Weah has said Ms Johnson-Sirleaf should not claim victory while his complaint to the Supreme Court is being investigated.
On Friday, Weah campaign officials filed a petition with the Supreme Court to halt vote counting.
But the court rejected the appeal and referred them to the National Elections Commission.
Ms Johnson-Sirleaf rejected claims of vote-rigging as absurd.
She told the BBC she hoped Mr Weah would join her new government after "getting over his disappointment".
The election was held after the civil war ended two years ago.