"The trilateral negotiations remain on track," Ramaphosa wrote on Twitter.
Sudan and Egypt both fear the $4 billion hydroelectric dam could lead to water shortages in their own countries.
The project has raised concerns in Egypt that already limited Nile waters will be further restricted. The Blue Nile is a tributary of the Nile from which Egypt gets 90% of its fresh water.
"It was agreed, at the conclusion of the summit, to continue negotiations and focus for the time being on giving priority to developing a binding legal agreement on the rules for filling and operating the Renaissance Dam," a statement issued by the Egyptian presidency said.
Ethiopia, which says it needs the dam to generate electricity for its people, has already achieved the first year of filling its dam due to the rainfall season in the area, the statement from Abiy's office said.
"The dam under construction is already overtopping," it said, adding that Ethiopia was committed to a "balanced and win-win" negotiation that ascertains that the river will benefit all the three countries involved.