The Supreme Court on Monday indefinitely delayed a vote for Liberia's new president, ordering the electoral commission to resolve an opposition party's complaint for fraud before the runoff can be held.
The decision throws Liberia's first democratic transition in seven decades into uncertainty.
Africa's first elected female leader, the Nobel laureate Ellen Johnson Sirleaf, is stepping down after transitioning her nation out of a long civil war.
Supreme Court Chief Justice Francis Korkpor said the National Elections Commission (NEC) was prohibited "from conducting the runoff election until the complaint filed by the petitioners is investigated", referring to the opposition Liberty Party.
Former international footballer George Weah and incumbent vice president Joseph Boakai were due to face each other in a runoff vote on Tuesday.
But they must now await the result of an ongoing NEC complaint as well as any Supreme Court appeal, which could take weeks.
The case was brought by Liberty Party presidential candidate Charles Brumksine, who came third on October 10 and has alleged ballot stuffing and false voter registration cards marred the election.
"Liberty Party has rested evidence fully and we, the National Elections Commission (NEC), will now take the stand.
"So in a matter of days, we hope that there can be some conclusion to the investigation," Musa Dean, a lawyer with the commission, said.
"Whoever is dissatisfied will come to the Supreme Court, and the Supreme Court will again hear their appeal. And thereafter, we'll set a date for the runoff," Dean explained.
Liberia's constitution sets out a legal maximum of 30 days following the lodging of a complaint by the NEC, meaning the body has until November 22 to resolve the Liberty Party's case, which was brought on October 23.
From then, the party has a week to appeal, and the Supreme Court a week to decide on the appeal.
The court also has the power to call new elections within 60 days if it decides to nullify the result.
The court found on Monday that the NEC had acted contrary to the law in declaring Weah and Boakai the top two candidates following an October 10 first round election while a question mark over the validity of the votes was pending.
"By setting a date and proceeding to conduct a runoff election without first clearing the complaint of the petitioners which alleged gross irregularities and fraud, the NEC was proceeding contrary to rules which are to be adhered to at all times," Korkpor said.
The court urged the commission to hear the Liberty Party's complaint and resolve it with "urgent attention", given the "critical" nature of the presidential vote.
Liberia is no stranger to disputed election results: Weah's CDC party challenged but ultimately accepted the results of presidential votes in 2005 and 2011.
The court case comes at a tense moment in Liberian politics, as Brumskine and Boakai have both accused incumbent President Ellen Johnson Sirleaf of "interference" in the elections and of secretly supporting Weah over her own vice president, claims she has strongly denied.
International donors have poured billions of dollars into Liberia since Sirleaf was elected in 2005, and remain nervous to see completed what will be the country's first democratic transition in seven decades.