WASHINGTON, D.C. —President Trump gave Saudi Arabia’s Crown Prince Mohammed bin Salman an ultimatum in an April 2 phone call to begin cutting oil production or he would be powerless to stop lawmakers from passing legislation to withdraw U.S. troops from the kingdom, four sources familiar with the matter told Reuters.

The message was delivered 10 days prior to the announcement of production cuts by the kingdom, and was part of a U.S. pressure campaign that led to a landmark global deal to slash oil supply as demand collapsed due to the coronavirus pandemic, a major diplomatic victory for the White House.

According to the report, bin Salman was so taken aback by the ultimatum that he ordered both aids out of the room so he could continue the discussion in private, a U.S. source who was briefed on the discussion by senior administration officials said.

Trump is reportedly working to protect the U.S. oil industry from a historic price meltdown as economies worldwide struggle and citizens stay home to fight the virus. Trump has previously criticized the oil cartel for raising energy costs for Americans with supply cuts that usually lead to higher costs at the pump.

Without production cuts, “there would be no way to stop the U.S. Congress from imposing restrictions that could lead to a withdrawal of U.S. forces,” the administration reportedly told Saudi leaders, according to a senior U.S. official. “We are defending your industry while you’re destroying ours,” the official said, summing up the argument as told to Saudi leaders.

When asked if he told the crown prince the U.S. might pull forces out of Saudi Arabia, Trump said, “I didn’t have to tell him.”

“I thought he and President Putin, Vladimir Putin, were very reasonable,” Trump added. “They knew they had a problem, and then this happened.”

He also said Russia and Saudi Arabia were having a hard time making a deal before he intervened.

Saudi Arabia’s government media office did not respond to a request for comment. A Saudi official who asked not to be named said the agreement represented the will of all countries in the so-called OPEC+ group of oil-producing nations, which includes OPEC plus a coalition led by Russia.

“Saudi Arabia, the United States and Russia have played an important role in the OPEC+ oil cut agreement, but without the cooperation of the 23 countries who took part in the agreement, it would not have happened,” said the official, who declined to comment on the discussions between U.S. and Saudi leaders.

The week before Trump’s phone call with bin Salman, Republican U.S. Senators Kevin Cramer and Dan Sullivan had introduced legislation to remove all U.S. troops, patriot missiles and anti-missile defense systems from the kingdom unless Saudi Arabia cut oil output.

Support for the measure had been gaining momentum as Congress fumed over the Saudi-Russia oil price war. Saudi Arabia re-opened production in April, flooding the global supply with crude oil after Russia refused to deepen production cuts in line with an earlier OPEC supply pact.

On April 12, under pressure from Trump, OPEC, Russia and other allied producers slashed production by 9.7 million barrels per day, or about 10 percent of global output.

Despite the massive cuts, oil prices continued to fall to historic lows.

The Untied States has about 3,000 troops in the country, and the U.S. Navy’s Fifth Fleet protects oil exports from the region.