Oil extended gains following a third monthly advance after OPECand Russia agreed to prolong production cuts through to the end of2018 in their fight against a global supply glut.

Futures added 0.8% in New York after rising 0.2% Thursday. Thenine-month extension was strengthened with the inclusion of Nigeriaand Libya, two OPEC members originally exempted from the curbs. Oilstockpiles in developed countries are still 150 million barrelsabove a five-year average, leaving OPEC and its allies with morework to do, Saudi Arabia's Energy Minister Khalid Al-Falih saidThursday.

Saudi Arabia and Russia displayed unprecedented unity in Viennaon Thursday with Al-Falih saying he and his Russian counterpartAlexander Novak stood “shoulder to shoulder.” The show offriendship sought to dispel fears flagged by Wall Street analystsabout Moscow's reluctance to keep its side of the bargain in theabsence of an exit strategy for the deal. Still, the ministers willhave their work cut out as their primary rival, the U.S., expandedoutput to another record last week.