After the Opec decision, one million barrels per day of crude oil production from Saudi Arabia will remain in place at least through April.
Brent crude was up 6 cents, or 0.1%, at $51.35 a barrel at 1450 GMT, after trading as high as $52.02 earlier in the session
OPEC+ had initially agreed in April that it would cut supply by 9.7 million barrels per day (bpd) during May-June to prop up prices that collapsed due to the coronavirus crisis.
An extension to cuts was contingent on high compliance, three Opec sources told Reuters
The meeting between Opec producers and allies was held on Sunday via videoconference in a last effort to establish a deal
The Organization of the Petroleum Exporting Countries is reducing output by about 1.2 million barrels per day as part of a deal with Russia