The U.S. has congratulated the people of Liberia on the successful conclusion of the presidential run-off election, and President-elect George Weah on his victory.
"We will continue to support the success of this historic democratic transition and the peace and prosperity of Liberia", the statement read.
Ekweremadu urged the former World Footballer of the Year "to reciprocate the enormous goodwill and confidence reposed in him by the good people of Liberia and the worldwide community by running an all-inclusive government".
"Democracy goes beyond election day, and if Liberia succeeds, West Africa succeeds, Africa succeeds, and the world succeeds".
The President, on behalf of the government and people of Nigeria, equally applauded the efforts of the country's National Election Commission, as well as regional and worldwide observers contributed immensely to the electoral process and the strengthening of post-conflict democracy in the West African country.
George Weah will take over from Ellen Johnson, who ruled for 12 years.
Buhari described Weah's victory as an affirmation of the will of the Liberian people to remain united, peaceful and prosperous.
Liberia's president-elect and ex-soccer star George Weah says he is "honored to join a new generation of heads of state". "All we are asking is for all Liberians to come together so we can build our country".
Weah played with AS Monaco and Paris Saint-Germain, among others.
Addressing supporters in Monrovia, Boakai promised to provide support to Weah, but he also reminded him of Liberia's fragile economy and the challenges that lie ahead.
Following a December 26 poll, Weah's Coalition for Democratic Change took 61.5 percent of the vote, beating Vice President Joseph Boakai's Unity Party, which got 38.5 percent.
French President Emmanuel Macron has called Liberia's president-elect George Weah to congratulate him and invite him to visit.
Weah's supporters are confident that he will better represent their interests, which they believe seasoned politician Sirleaf failed to address after more than a decade in office.
With more than 98 percent of votes counted late Thursday, Weah received 61.5 percent of ballots while Vice President Joseph Boakai received 38.5 percent.
The 51-year-old Weah, a senator who entered politics after his 2002 retirement, led the first-round election in October but didn't receive enough votes to win outright.