It’s a pretty good bet that you are going to pay more to fill up your gas tank as we head into the summer driving season.

Prices are rising rapidly, including a 5-cent per gallon increase in the space of five days this past week. And among other factors, you can thank President Donald Trump and his tightened sanctions on Iran for that.

Trump is so concerned that his sanctions will raise gasoline prices that on Friday he said he “called up” the Organization of the Petroleum Exporting Countries and told them to bring down oil prices. The president has lobbied OPEC hard in the past to pump enough oil to keep U.S. gasoline prices low.

It’s a state of affairs that reeks of irony.

U.S. independence from Middle East oil has stood at the forefront of national ambitions since the 1970s, when oil prices went wild and the economy went into a long and painful funk.

Almost five decades and an economic transformation later, vehicle gas mileage has vastly improved, buildings are becoming more energy-efficient, we have a growing renewable-energy sector and, incredibly, the U.S. produces more oil and natural gas than ever. We even export some, though we are still a net importer.

And guess what.

The Saudis are in control again, thanks to the Trump administration’s sanctions on Iran and the Venezuelan crisis. Throw in some uncertainty in unstable producer states such as Libya and Nigeria, and the world markets may once again need Saudi Arabia to ride to the rescue.

“We are really at the mercy of Saudi Arabia like never before, even going back to the 1970s,” said John Kilduff of the Again Capital investment firm.

If the Saudis so desire, they can tighten their taps, slow the flow of oil and send prices high enough to impair global economic growth. It’s all up to them.

Trump’s Iran policy “is clearly beneficial for the Saudis,” according to an analyst report issued Tuesday by Raymond James, a financial services firm.

And that’s squeezing American drivers at the pump. According to the American Automobile Association, the national average price for regular gasoline Friday was $2.88 a gallon, about 25 cents more than a month ago. The average was $4.04 in California, the most expensive gas in the country. The cheapest was in Alabama, at $2.51.

“I don’t think a $3 per gallon national average is impossible,” said Stewart Glickman, an analyst with CFRA Research.

A barrel of oil was at a six-month high Thursday, but fell Friday after Trump said that he had called OPEC. The two big benchmarks, West Texas Intermediate and Brent crude, were at $62 and $71, respectively on Friday morning. That’s roughly a 4% drop in a day. Analysts said part of the reason for the drop was a rumor that China would be exempted from the Iran sanctions.

The sweet spot is about $80. That is a price at which producers such as Saudi Arabia can make plenty of money without creating outrage and economic strain among customers. You get much above $80 per barrel — and look out.

The rule of thumb is that a sustained $10 increase in the price of a barrel of oil shaves a half-point off the U.S. gross domestic product.

“It acts like a tax on American consumers,” Kilduff said of expensive oil. “It hurts consumer confidence, can damage India’s and Asia’s economies. It will knock Japan, China and Europe into a recession because you are forced to spend money on energy and not on leisure, housing, furniture, clothing.”

So how did we get here?

First, realize that world oil supply and demand are tightly in sync at about 100 million barrels a day. There isn’t much room for error on either side.

A disruption in the world oil market, no matter how small, can send a ripple through prices that will be felt at gas pumps across the country and at the many homes in the Northeast that burn oil to remain toasty during the winter.

If much of that production goes offline, let’s say a million barrels or so, the effect on the world economy will follow within a month or two.

At the moment, the primary disruption is in Iran. It exported about 2.3 million barrels of oil a day at its peak. But production has dropped to 1.3 million and is headed significantly lower because of Trump administration sanctions intended to scare off Iran’s remaining customers and drive its oil exports down to zero. (Trump wants Iran to stop supporting terrorists, to halt missile development and to renegotiate parts of the international nuclear treaty that the United States withdrew from last year.)

The Iran sanctions were imposed last fall, but Trump granted waivers to several countries, allowing them to continue buying Iranian crude. At the time, he was using Twitter messages to urge OPEC, and Saudi Arabia in particular, to pump more oil so that oil prices would stay affordable.

The Saudis and other exporting nations complied with Trump’s request, which analysts said was a “bait and switch” move that left the world awash in oil. Oil prices plummeted, and major producers fumed.

Now China, India, Japan, South Korea and Turkey — all significant U.S. trading partners — have been told that waivers won’t be renewed in May, exposing the five countries to economic penalties if they continue buying Iranian crude.

Meanwhile, Venezuelan oil production has also fallen off a cliff, because of that country’s civil unrest and the mismanagement of its national oil company, Petróleos de Venezuela (PDVSA).

The trick for consumer nations is to replace that Iranian and Venezuelan oil. And the only country that can expand its production on short notice — and avert a rise in global oil prices — is Saudi Arabia, with its of 201 billion barrels of oil under the desert. (Five times U.S. proven reserves.)

“The Saudis are the ones with the major spare capacity out there,” Glickman said. “Right now, they are producing around 9.8 million barrels per day. They have been as high as 11.3 [million], so it would not take a lot of effort to add 1.2 million a day and could probably add as much as 1.5 million if they wanted.”

Glickman added: “This matters because you are leaving yourself dangerously thin if there is some supply shock. And the global oil market likes to have spare capacity in case Libya goes down or Nigeria goes down or Venezuela goes to zero.”

The Saudis are smarting from Trump’s “bait and switch.” And they would probably love to have oil trade at $80 a barrel to help them meet the demands of the kingdom’s people. On the other hand, Trump has supported Mohammed bin Salman, the kingdom’s 33-year-old crown prince and de facto ruler, in the aftermath of the Oct. 2 murder of Washington Post columnist Jamal Khashoggi by Saudi agents inside the Saudi Consulate in Istanbul.

“It’s hard to believe that they won’t get pushed around by President Trump, given all the cover Trump has given Saudi Arabia and the crown prince over the Khashoggi affair,” Kilduff said. “There is a huge debt that exists and is owed by the Saudis to the Trump administration.”

But even with an ocean of oil at their disposal, the Saudis have a difficult time managing the supply. Sometimes they cut production too much and prices skyrocket.

“It tends to get away from them, both on the upside and downside,” Kilduff said. “But either way, the Saudis are in the driver’s seat.”

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