The presidents of Ivory Coast and Ghana reached a deal on Monday in talks on a maritime border dispute that had frozen new oil drilling in a contested area, mediator Kofi Annan told Reuters.

"We have a deal," the former U.N. secretary general told Reuters, as he wrapped up the talks in Geneva. He did not elaborate and officials did not immediately disclose the terms of the agreement.

It appeared to have been reached quickly. Ivory Coast's presidency said President Alassane Ouattara had left Abidjan on Sunday for the discussions with his Ghanaian counterpart John Dramani Mahama.

An international tribunal ruled last month that Ghana could continue developing a $4.9 billion offshore oil project in the area but imposed a ban on new drilling.

The decision by the Hamburg-based International Tribunal for the Law of the Sea was regarded as positive for Ghana and British oil firm Tullow, which leads a consortium developing the TEN field, where it has already drilled the wells it needs to start production.

The tribunal did not judge the merits of the dispute and the court is expected to make a final ruling in 2017.

Analysts have said that precedent suggests it is unlikely to redraw the current equidistant maritime boundary.