The two countries signed an intergovernmental cooperation agreement for the Grand Tortue/Ahmeyim gas field, which straddles their shared maritime border.
The gas field is estimated to hold 450 billion cubic metres (nearly 16 trillion cubic feet) of gas. Senegal, announcing its discovery in January 2016, described it as the biggest offshore gas deposit in West Africa.
The agreement was signed on the second day of a trip to the Mauritanian capital Nouakchott by Senegalese President Macky Sall, an AFP reporter saw.
An official at the Mauritanian ministry for oil, energy and mines said the accord covers “development of the exploitation and sharing of resources” of the field as well as a dispute settlement procedure.
Sall visited Mauritania on the heels of protests in northern Senegal after a young local fisherman was killed by coastguards in Mauritanian waters.
He and Mauritanian President Mohamed Ould Abdel discussed “conditions for exploiting fishing resources,” according to a joint communique, but no agreement on the spat was announced.
Instead, they called on fishery ministers “to take every precaution to strengthen cooperation in this area, with a view to signing a protocol of agreement by the end of March 2018”.