The Peace Corps pulled out of Liberia, which was founded in the 19th century by freed black slaves from America, when civil war broke out in 1989. The war killed around 200,000 people.

Warlord Charles Taylor, who started the conflict, was voted president in 1997 but chased into exile in 2003 by a subsequent rebellion, paving the way for former World Bank economist Ellen Johnson Sirleaf's election. Taylor is on trial for war crimes.

"The return is an important milestone. It signifies the confidence the U.S. government has in Liberia's recovery and stability," a Foreign Ministry statement quoted Brooks Robinson, charge d'affaires at the U.S. embassy, as saying after signing an agreement on Friday.

Established in 1961, the Peace Corps has more than 8,000 volunteers spread across 139 countries working mainly to improve education and healthcare.

Most are youngsters who volunteer after finishing college, and they are known in West Africa for living in small groups, often in isolated villages, and learning the tribal languages of the people they work among.