Liberia is assuming responsibility for its security for the first time since civil war ended in the West African country 13 years ago, a move welcomed by U.N. Secretary-General Ban Ki-moon.

A U.N. peacekeeping force transferred responsibilities Thursday, and President Ellen Johnson Sirleaf will mark the handover on Friday.

A reduced U.N. force of about 1,200 troops will remain in a supporting role.

Ban paid tribute to Liberia's determination "to work towards lasting peace," his spokesman said.

The peacekeeping force was deployed in 2003 to help stabilize Liberia after a four-year civil war. That conflict and a previous civil war are said to have killed more than 250,000.

During the Ebola virus outbreak in 2014, Liberia's U.N. ambassador called a strong international presence in the country "a critical stabilizing factor."