MONROVIA, Liberia — After allegations of election fraud and a delayed runoff that raised fears about a constitutional crisis, Vice President Joseph Boakai of Liberia accepted defeat in the country’s presidential election on Friday and offered his support to the new government.

“I congratulate the winner, Ambassador George Manneh Weah, and pray that God will guide and guard him as he takes upon the onerous responsibility of steering the affairs of our nation,” Mr. Boakai said outside his party’s headquarters in Monrovia.

By conceding the race to Mr. Weah, a former international soccer star, Mr. Boakai helped pave the way for the first democratic transition of power in the West African country in more than 70 years. President Ellen Johnson Sirleaf is stepping down after two terms as Africa’s first democratically elected female president.

The National Election Commission announced on Friday that Mr. Weah had won with 61.5 percent of the vote. Turnout was low, with around 56 percent of registered voters casting ballots, in part because the election was scheduled for the day after Christmas.