Oil tumbled by the most in two months after output talks on Sunday between the world’s biggest producers ended without any agreement on limiting supplies, a diplomatic failure that threatens to renew the rout in prices.

Futures fell as much as 6.8% in New York, the biggest intraday drop since 1 February. The summit in the Qatari capital, which dragged on for more than ten hours beyond its initially scheduled conclusion, finished with no final accord. Discussions stumbled after Saudi Arabia and other Gulf nations wouldn’t agree to any deal unless all Opec members joined including Iran, which wasn’t present at the meeting, Russian energy minister Alexander Novak told reporters.

“The weekend talks are demonstration that the Saudi government, as the deputy crown prince has clearly stated, doesn’t want to cede market share,” said Ed Morse, head of global commodity research at Citigroup Inc. by phone. “They are fearful that the world may be in a weak or bearish market for a long period of time. In a bear market, as they learned from the 1980s, if they cede market share it is very difficult to get it back.”

West Texas Intermediate for May delivery lost as much as $2.75 to $37.61 a barrel on the New York Mercantile Exchange and was at $38.11 at 8:52 a.m. Hong Kong time. The contract fell $1.14, or 2.8%, to $40.36 on Friday. Total trading volume was more than fivefold the 100-day average.

Brent for June settlement dropped as much as $3, or 7%, to $40.10 a barrel on the London-based ICE Futures Europe exchange. The contract lost 74 cents, or 1.7%, to $43.10 on Friday. The global benchmark was at a $1.46 premium to WTI for June.

Oil ministers from 16 nations, representing about half the world’s output, gathered in the Qatari capital in a bid to stabilize the global market, the first significant attempt at coordinating oil output between the Organization of Petroleum Exporting Countries and nations outside the group in 15 years. There were significant hurdles to any deal after Saudi Arabia’s Deputy Crown Prince Mohammed bin Salman said the kingdom wouldn’t restrain its production without commitments from other major producers including Iran, which has ruled out freezing for now.

The world’s largest oil exporter could increase output to 11.5 million barrels a day immediately and go to 12.5 million in six to nine months “if we wanted to,” the prince said. The kingdom pumped 10.2 million barrels a day last month, according to data compiled by Bloomberg.

Iran, which is reviving oil exports after international sanctions were lifted in January, ruled out any limits on its output before reaching pre-sanctions levels, dismissing the notion of joining the freeze as “ridiculous.” The nation’s oil minister Bijan Namdar Zanganeh said Saturday he wouldn’t attend the Doha talks and won’t be a signatory to any deal as it would amount to self-imposed sanctions.

“The fact that Saudi Arabia seems to have blocked the deal is an indicator of how much its oil policy is being driven by the ongoing geopolitical conflict with Iran,” said Jason Bordoff, director of the Center on Global Energy Policy at Columbia University and a former White House official.