HOUSTON — Oil-producing nations on Sunday agreed to the largest production cut ever negotiated, in an unprecedented coordinated effort by Russia, Saudi Arabia and the United States to stabilize oil prices and, indirectly, global financial markets.

Saudi Arabia and Russia typically take the lead in setting global production goals. But President Trump, facing a re-election campaign, a plunging economy and American oil companies struggling with collapsing prices, took the unusual step of getting involved after the two countries entered a price war a month ago. Mr. Trump had made an agreement a key priority.

It was unclear, however, whether the cuts would be enough to bolster prices. Before the coronavirus crisis, 100 million barrels of oil each day fueled global commerce, but demand is down about 35 percent. While significant, the cuts agreed to on Sunday still fall far short of what is needed to bring oil production in line with demand.

The plan by OPEC, Russia and other allied producers in a group known as OPEC Plus will slash 9.7 million barrels a day in May and June, or close to 10 percent of the world’s output.