Earlier in the day, Mr. Boakai’s traded confrontation for conciliation in making what he said was a decision for the good of the country, and dismissing the idea of challenging the results in court.
“I reject any temptation of imposing pain, hardship, agony and uncertainty on our people,” he said, alluding to past conflicts in Liberia’s transitions of power. “My name will not be used as an excuse for one drop of human blood to be spilled in this country.”
“It has never been about me, it has always been and should always be about Liberia,” he added, urging Liberians to reconcile.
Mr. Weah is expected to take office in January.
When preliminary results pointing to Mr. Weah’s victory were announced, Liberians took to the streets and cheered. Many returned to the streets after Mr. Boakai’s concession speech.
Mr. Weah, a senator who also ran for president in 2005 and for vice president in 2011, placed first in a crowded field in the first round of voting, winning 38.4 percent of the votes. Though his support was stronger than most analysts had expected, it was not enough to win outright.
As the date of the runoff approached, Mr. Boakai and his supporters in the governing Unity Party asserted that Mrs. Sirleaf had interfered in the election, accusations that she denied. The vice president and the third-place candidate, who won just under 10 percent, took their case to the Liberian Supreme Court, delaying the final vote by two months.
The election’s peaceful conclusion was seen by some as a milestone for the fledgling democracy, which was founded almost two centuries ago by freed American slaves but has not seen a peaceful transition of power since 1944.
Ibrahim al-Bakri Nyei, 30, a doctoral student in Liberian politics, came of age during a 14-year civil war that left 250,000 dead and the nation’s infrastructure destroyed. On Friday, he said he was “very proud.”
“It builds my confidence in the future of my country that I will also have the opportunity to participate in the democratic process,” he said, adding, “If members of my generation are to ascend to power, it should not be through the barrel of a gun.”