Saudi Aramco told Asian refiners it will suspend a supply flexibility clause - known as operational/lifting tolerance - from January until further notice - sources.
Aramco tells customers the move is in line with the Saudi government's decision to reduce output as part of OPEC supply cuts.
Operational/lifting tolerance usually allows customers to request 5-10 percent more crude than the volumes allocated by Aramco in case they need more oil.
Last week, Saudi Aramco told its U.S. and European customers it will reduce supply from January.
Reduction of supply to Asia is expected to be smaller than to the United States or Europe.
(Reporting by Nidhi Verma; Editing by Susan Fenton)