The agreement marks the first direct commitment from both sides since rebels seized key cities in eastern Congo.

DAKAR, Senegal — The Democratic Republic of Congo and Rwanda-backed rebels have signed a declaration of principles for a permanent ceasefire in eastern Congo, where ethnic tensions and a quest for rich minerals have resulted in one of Africa’s longest conflicts, with thousands killed this year alone.

Democratic Republic of Congo and the M23 rebel group pledged to sign a peace agreement by August 18, at a ceremony in Doha on Saturday, a sign of progress even as outstanding details need to be negotiated.