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Now, oil prices had been falling for months due to a glut of crude. Many analysts said a slowing global economy would reduce demand for oil. But the attacks on these two tankers sent oil prices up sharply. NPR's Jim Zarroli looks at why that is and whether that upward climb will last.
JIM ZARROLI, BYLINE: There is no more important waterway for the energy industry than the 21-mile-wide Strait of Hormuz. It links the Persian Gulf and the Gulf of Oman, and oil-rich countries such as Saudi Arabia use it to send their oil around the world.
Roger Diwan is an oil analyst at IHS Markit.
ROGER DIWAN: It's really the main chokepoint of oil exports in the world. It's about 16, 17 million barrels of crude oil go through that every day.
ZARROLI: And it's not just oil that uses the waterway. Liquefied natural gas from Qatar passes through, and so do petrochemicals. Diwan says, as a result of these attacks, shipping in the region has almost come to a standstill.
DIWAN: A lot of ships are slow sailing, stopped, or some of them are returning home. So it's paralyzing a little bit - the traffic - until we know exactly what happened.
ZARROLI: And that's a big potential problem for the global economy. Countries such as China and Japan rely heavily on oil from the Middle East. The United States, by contrast, has become a lot more energy independent than it once was. But that doesn't mean Americans have nothing to fear from today's attacks.
For one thing, oil is a global commodity. So if supply is threatened in Saudi Arabia, prices for oil from Texas go up as well. And there's another issue. Some of that oil coming through the Strait of Hormuz ends up in the United States.
Amy Myers Jaffe of the Council on Foreign Relations says American refineries are designed for just the kind of heavy crude that comes out of the Gulf.
AMY MYERS JAFFE: We now have a situation where it's harder for U.S. refiners in Texas and along the coast in Louisiana to find this very specific heavier oil that they need to refine.
ZARROLI: Insurance rates for cargo ships have already begun to rise today. That will increase costs for oil producers and put pressure on prices. So Jaffe says there's a lot to be concerned about here. And she says oil investors may actually be underestimating the risks from the current friction in the Gulf. A month ago, another series of attacks occurred against tankers in the Gulf. Prices shot up, but within a short period, they fell back even further - and they kept falling.
JAFFE: You know, it's hard to get the price of oil to go up right now because everybody is so focused on the negative effect of the trade war on oil.
ZARROLI: Investors right now are fixated on the slowing global economy and the impact of the trade war between the United States and China, and that has been driving down prices. But today's attacks sent prices in the opposite direction, climbing as much as 4%. That's a reminder of how volatile politics are in the Middle East and the pressure that can put on oil prices. Jim Zarroli, NPR News, New York. Transcript provided by NPR, Copyright NPR.