Iran, Saudi Arabia’s longstanding rival in OPEC, is a complicating factor. The Iranians reacted angrily to news reports of Mr. Hook’s presence in Vienna. The diplomat has been traveling the world to build support for America’s latest sanctions against Iran.
The Iranian oil minister, Bijan Zanganeh, criticized Mr. Hook’s discussions as “unprofessional” and “interfering,” according to the Iranian news agency IRNA, and said that OPEC was an independent body that did not take orders from the United States, which is not a member.
Mr. Zanganeh also told reporters before the beginning of the meeting on Thursday that Iran would not accept a cut beyond what was already being reduced by sanctions.
Saudi Arabia, the world’s largest exporter, and Russia, which also produces about 12 percent of the world output, increasingly see their interests aligned. Production cuts in late 2016 lifted prices to the point that Saudi Arabia and Russia were persuaded in June to open up the taps. The move was partly a response to Mr. Trump’s complaints at the time about rising prices.
“What this confirms is that you need to have Russia in place to have a credible deal,” Mr. Diwan said.
Russia’s energy minister, Alexander Novak, did not attend the meeting on Thursday, but was expected to be at the session on Friday.
The oil market’s focus, though, quickly shifted from possible supply shortages to worries about a potential glut caused, among other things, by a slowing world economy and unexpectedly robust output from the United States.
The U.S. Energy Information Administration reported on Thursday that last week the United States had become a net exporter of oil, gasoline and other refined fuels for the first time in 75 years, a notable, if potentially fleeting, distinction.