In an April 2 phone call, Trump told Saudi Crown Prince Mohammed bin Salman that unless the Organization of the Petroleum Exporting Countries (OPEC) started cutting oil production, 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 threat to upend a 75-year strategic alliance, which has not been previously reported, was central to the U.S. pressure campaign that led to a landmark global deal to slash oil supply as demand collapsed in the coronavirus pandemic — scoring a diplomatic victory for the White House.

Trump delivered the message to the crown prince 10 days before the announcement of production cuts. The kingdom’s de facto leader was so taken aback by the threat that he ordered his aides out of the room so he could continue the discussion in private, according to a U.S. source who was briefed on the discussion by senior administration officials.

The effort illustrated Trump’s strong desire to protect the U.S. oil industry from a historic price meltdown as governments shut down economies worldwide to fight the virus. It also reflected a telling reversal of Trump’s longstanding criticism of the oil cartel, which he has blasted for raising energy costs for Americans with supply cuts that usually lead to higher gasoline prices. Now, Trump was asking OPEC to slash output.

A senior U.S. official told Reuters that the administration notified Saudi leaders that, 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 official summed up the argument, made through various diplomatic channels, as telling Saudi leaders: “We are defending your industry while you’re destroying ours.”

Reuters asked Trump about the talks in an interview Wednesday evening at the White House, at which the president addressed a range of topics involving the pandemic. Asked if he told the crown prince that 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 said. “They knew they had a problem, and then this happened.”

Asked what he told the Crown Prince Mohammed, Trump said: “They were having a hard time making a deal. And I met telephonically with him, and we were able to reach a deal” for production cuts, Trump said.

Saudi Arabia’s government media office did not respond to a request for comment. A Saudi official who asked not to be named stressed that 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 Saudi official, who declined to comment on the discussions between U.S. and Saudi leaders.

The week before Trump’s phone call with Crown Prince Mohammed, U.S. Republican Sens. 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 was gaining momentum amid Congressional anger over the ill-timed Saudi-Russia oil price war. The kingdom had opened up the taps in April, unleashing a flood of crude into the global supply after Russia refused to deepen production cuts in line with an earlier OPEC supply pact.

On April 12, under pressure from Trump, the world’s biggest oil-producing nations outside the United States agreed to the largest production cut ever negotiated. OPEC, Russia and other allied producers slashed production by 9.7 million barrels per day (bpd), or about 10% of global output. Half that volume came from cuts of 2.5 million bpd each by Saudi Arabia and Russia, whose budgets depend on high oil-and-gas revenues.

Despite the agreement to cut a tenth of global production, oil prices continued to fall to historic lows. U.S. oil futures dropped below $0 last week as sellers paid buyers to avoid taking delivery of oil they had no place to store. Brent futures, the global oil benchmark, fell towards $15 per barrel — a level not seen since the 1999 oil price crash — from as high as $70 at the start of the year.

The deal for supply cuts could eventually boost prices, however, as governments worldwide start to open their economies and fuel demand rises with increased travel. Whatever the impact, the negotiations mark an extraordinary display of U.S. influence over global oil output.

Cramer, the Republican senator from North Dakota, told Reuters he spoke to Trump about the legislation to withdraw U.S. military protection from Saudi Arabia on March 30, three days before the president called Crown Prince Mohammed.

Asked whether Trump told Saudi Arabia it could lose U.S. military support, U.S. Energy Secretary Dan Brouillette told Reuters the president reserved the right to use every tool to protect U.S. producers, including “our support for their defense needs.”

The strategic partnership dates back to 1945, when President Franklin D. Roosevelt met with Saudi King Abdul Aziz Ibn Saud on the USS Quincy, a Navy cruiser. They reached a deal: U.S. military protection in exchange for access to Saudi oil reserves. Today, the United States has about three thousand troops in the country, and the U.S. Navy’s Fifth Fleet protects oil exports from the region.

Saudi Arabia relies on the United States for weapons and protection against regional rivals such as Iran. The kingdom’s vulnerabilities, however, were exposed late last year in an attack by 18 drones and three missiles on key Saudi oil facilities. Washington blamed Iran; Tehran denied it.

Thirteen angry senators

Trump initially welcomed lower oil prices, saying cheap gasoline prices were akin to a tax cut for drivers.

That changed after Saudi Arabia announced in mid-March it would pump a record 12.3 million bpd — unleashing the price war with Russia. The explosion of supply came as governments worldwide issued stay-home orders — crushing fuel demand - and made clear that U.S. oil companies would be hit hard in the crude price collapse. Senators from U.S. oil states were infuriated.

On March 16, Cramer was among 13 Republican senators who sent a letter to Crown Prince Mohammed reminding him of Saudi Arabia’s strategic reliance on Washington. The group also urged Commerce Secretary Wilbur Ross to investigate whether Saudi Arabia and Russia were breaking international trade laws by flooding the U.S. market with oil.

On March 18, the senators – a group that included Sullivan of Alaska and Ted Cruz of Texas — held a rare call with Princess Reema bint Bandar bin Sultan, the Saudi ambassador to the United States. Cramer called the conversations “brutal” as each senator detailed the damage to their states’ oil industries.

“She heard it from every senator; there was nobody that held back,” Cramer told Reuters.

The Saudi embassy did not respond to requests for comment.

Cramer said the princess relayed their comments to officials in Saudi Arabia, including the energy minister. The senators told the princess that the kingdom faced rising opposition in the Senate to the Saudi-led coalition that is waging a war in Yemen against Houthi rebels.

Saudi and U.S. officials have said the Houthis are armed by Iran, which Tehran denies. The backing of Senate Republicans over Yemen had proved crucial for Saudi Arabia last year. The Senate upheld Trump vetoes of several measures seeking to end U.S. weapons sales and other military support to Saudi Arabia amid outrage over the Yemen conflict, which has caused more than 100,000 deaths and triggered a humanitarian crisis.

Cramer said he made a phone call to Trump on March 30, about a week after he and Sullivan introduced their bill to pull U.S. troops from Saudi Arabia. The president called Cramer back the same day with Energy Secretary Brouillette, senior economic adviser Larry Kudlow and U.S. Trade Representative Robert Lighthizer on the call, the senator said.

“I said the one person that you don’t have on the call that can be very helpful is Mark Esper,” the defense secretary, Cramer recounted, saying he wanted Esper to address how U.S. military assets in Saudi Arabia might be moved elsewhere in the region to protect U.S. troops.

The Pentagon did not respond to a request for comment on whether Esper was involved in discussions of pulling military assets out of Saudi Arabia.

Bending the knee

Trump’s oil diplomacy came in a whirlwind of calls with Saudi King Salman, Crown Prince Mohammed and Russian President Vladimir Putin starting in mid-March. The Kremlin confirmed Putin’s conversation with Trump and said they discussed both oil supply cuts and the coronavirus pandemic.

On the April 2 call with Prince Mohammed, Trump told the Saudi ruler he was going to “cut them off” the next time Congress pushed a proposal to end Washington’s defense of the kingdom, according the source with knowledge of the call. Trump also publicly threatened in early April to impose tariffs on oil imports from Saudi Arabia and Russia.

After the conversation with the Saudi crown prince, and another the same day with Putin, Trump tweeted that he expected Saudi Arabia and Russia to cut output by about 10 million barrels, which “will be GREAT for the oil & gas industry!”

Riyadh and Moscow later confirmed they had restarted negotiations.

On April 3, Trump hosted a meeting at the White House with senators Cramer, Cruz, and Sullivan, and oil executives from companies including Exxon Mobil Corp., Chevron Corp., Occidental Petroleum Corp. and Continental Resources .

During the public portion of the meeting, Cramer told Trump that Washington can use the billions of dollars it spends defending Saudi Arabia on other military priorities “if our friends are going to treat us this way.”

The prospect of losing U.S. military protection made the royal family “bend at the knees” and bow to Trump’s demands, a Middle Eastern diplomat told Reuters.

After prolonged and fractious negotiations, top producers pledged their record output cut of 9.7 million bpd in May and June, with the understanding that economic forces would lead to about 10 million bpd in further cuts in production from other countries, including the United States and Canada.

Trump hailed the deal and cast himself as its broker. “Having been involved in the negotiations, to put it mildly, the number that OPEC+ is looking to cut is 20 Million Barrels a day…” he tweeted shortly after the deal.

Riyadh also took credit. Saudi energy minister Prince Abdulaziz told Reuters at the time that the crown prince had been “instrumental in formulating this deal.”