Scott D. Sheffield, chairman of Pioneer Natural Resources, a major Texas oil producer, said if there were a significant decline in Venezuelan and Iranian exports, “and Saudi doesn’t increase output, we’re going to see $100 oil by the end of the year.”

Just a few years ago, $100 a barrel was considered normal. But prices collapsed in 2014, falling in the United States to below $30 in early 2016, as a glut of oil filled up tankers. Now the world’s big oil producers are seeking a sweet spot for oil prices.

American and global oil prices rose modestly on Wednesday despite Mr. Trump’s criticism.

Even as he has criticized OPEC, Mr. Trump has found a willing ally in Saudi Arabia. Riyadh has long argued against the Iran nuclear deal, and pressed the United States to put more pressure on the Shiite Islamic regime. The Saudis are fighting Houthi rebels backed by Iran in neighboring Yemen and have been trying to counter Iranian influence in Syria and elsewhere.

Iran would like higher oil prices, because it needs money to invest in its weakened oil industry and ailing economy. But its exports could falter with the return of sanctions that were removed under the nuclear deal. And other OPEC members will seek to take advantage of Iran’s misfortune by selling more oil to big markets like China and India.

“If you are the Saudis, you want to do Trump a favor and get him off your back,” said Robert McNally, president of Rapidan Energy Group, a consulting firm.

Sadad Ibrahim Al Husseini, a former executive vice president of Saudi Aramco, said Russian and Saudi Arabian leaders “will look at gradual but steady increases of overall supply, easily between one and 1.2 million barrels a day by year-end.”

The two countries will probably lobby other oil-producing nations to also raise output, particularly Kuwait and United Arab Emirates, both OPEC members.