The resignation of South African President Thabo Mbeki is a "big loss" for Africa, African Union chairperson Jakaya Kikwete said on Monday.

"It is quite sad, because he was one of those prominent leaders. He has strong commitments to Africa's development," Kikwete said on the sidelines of the UN General Assembly in New York.

"Nepad (New Partnership for African Development) is actually his brain child. It is a big loss for Africa to loose such a prominent leader," said Kikwete who is also Tanzania's president.

Nepad is a club of African leaders to promote democracy and good governance.

Operating under the aegis of Nepad is a project dubbed the African Peer Review Mechanism (APRM), where governments voluntarily open themselves up to scrutiny by fellow African leaders.

Mbeki announced his departure on Sunday under pressure from his ruling African National Congress party, which on Monday named its deputy chief Kgalema Motlanthe to succeed him.

Mbeki (66) succeeded Nelson Mandela as president in June 1999. His term was due to expire in mid-2009, and he has largely been seen as a lame duck president since losing the ANC leadership to Zuma in December.

Mbeki has thus become the country's first democratically-elected president to be forced out of office before the end of his term.

The nomination for a new head of state is expected to be made in the ANC- dominated Parliament on Tuesday, with the vote and swearing in of the new president planned for Thursday.

Motlanthe, who like many of South Africa's current leaders was involved in the struggle to end white minority rule, is to serve as head of state until national elections are held in seven months' time.

Sapa