Qatar has announced it is pulling out of the OPEC oil producers' cartel, just days before the group meets in Vienna.
The Gulf state, which joined OPEC in 1961, said it would leave the cartel in January and would focus on gas production.
Qatar, the world's biggest exporter of liquefied natural gas, has been boycotted by some Arab neighbours over allegations that it funds terrorism.
OPEC is expected to cut oil supply at this week's meeting.
In early trading on Monday, Brent crude was $2.60 higher at $62.06 a barrel, while US West Texas Intermediate oil rose $2.42 to $53.35 a barrel.