Oil prices jumped more than 8 % on Wednesday to a five-week high as some of the world's largest oil producers agreed to curb oil output for the first time since 2008 in a last-ditch bid to support prices.
Brent crude futures for delivery in January were up $3.86, or 8.3 %, at $50.214 a barrel by 1405 GMT (09:05 a.m. EDT), recovering from a drop of nearly 4 % on Tuesday and on course for their biggest one-day move in nine months. Brent crude for delivery in February was up $3.94 at $51.26 a barrel.
U.S. West Texas Intermediate (WTI) crude futures were $3.66 higher at $48.89 a barrel, a one-week high.
The Organization of the Petroleum Exporting Countries has agreed its first output limiting deal in eight years, an OPEC source told Reuters as the debates continued in Vienna on the exact size of each member's cuts.
Key OPEC member Saudi Arabia said it was prepared to accept "a big hit" on its own production and agree to arch-rival Iran freezing output at pre-sanctions levels.
"It does rather look as though OPEC is going to come to an agreement," said Colin Smith, director of oil and gas research at Panmure Gordon in London.
A preliminary agreement struck in Algiers in September set an output cap at around 32.5-33 million barrels per day compared with the current 33.64 million bpd.
Before Wednesday's meeting, Saudi Energy Minister Khalid al-Falih said OPEC was indeed focusing on reducing output to a ceiling of 32.5 million bpd and hoped Russia and other non-OPEC producers would contribute a cut of another 0.6 million bpd.
"The extent of the (price) move shows no one wants to miss the boat. There must be a general consensus that there will be a cut, whether it's going to be bullish, I don't know, but it's the domino effect," PVM Oil Associates analyst Tamas Varga said.
Traders said markets were jittery and prices could swing sharply in either direction depending on developments in Vienna.
Iran and Iraq have been resisting pressure from Saudi Arabia to curtail production, making it harder for the group to reach an agreement on output cuts.
Analysts at Goldman Sachs, Barclays, and ANZ said oil prices would quickly fall to the low $40s a barrel if OPEC fails to strike a deal to cut output.