What to know about the Strait of Hormuz, a key passageway essential for global energy supply

Any disruption to traffic through the Strait of Hormuz is highly disruptive to the oil trade.

“The scale of what is at stake cannot be overstated,” said Hakan Kaya, senior portfolio manager at investment management firm Neuberger Berman. He said a partial slowdown lasting a week or two could be absorbed by oil companies. But a full or near full closure lasting a month or more would push crude oil prices, trading around $70 on Monday, “well into triple digits” and European natural gas prices “toward or above the crisis levels seen in 2022.”

Here’s what to know about the strait and the widening Iran war.

A key waterway for global shipping

The Strait of Hormuz is a bending waterway, about 33 kilometers (21 miles) wide at its narrowest point. It connects the Persian Gulf to the Gulf of Oman. From there, ships can then travel to the rest of the world. While Iran and Oman have their territorial waters in the strait, it's viewed as an international waterway all ships can ply. The United Arab Emirates, home to the skyscraper-studded city of Dubai, also sits near the waterway.

The strait long has been important for trade

The Strait of Hormuz through history has been important for trade, with ceramics, ivory, silk and textiles moving from China through the region. In the modern era, it is the route for supertankers carrying oil and gas from Saudi Arabia, Kuwait, Iraq, Qatar, Bahrain, the UAE and Iran. The vast majority of it goes to markets in Asia, including Iran's only remaining oil customer, China.

While there are pipelines in Saudi Arabia and the UAE that can avoid the passage, the U.S. Energy Information Administration says “most volumes that transit the strait have no alternative means of exiting the region.”

Threats to the route have spiked global energy prices in the past, including during the Israel-Iran war in June.

Is the strait closed?

The strait is not officially closed, but tanker traffic has dropped sharply as satellite navigation systems were disrupted, data and analytics firm Kpler said on X on Sunday. The U.K. Maritime Trade Operations Center reported attacks on several vessels in the area on either side of the strait and warned of elevated electronic interference to systems that show where ships are.

A bomb-carrying drone boat struck a Marshall Islands-flagged oil tanker in the Gulf of Oman, which leads into the strait from the east, killing one mariner, Oman said.

Iran has been threatening vessels approaching the Strait of Hormuz and is believed to have launched multiple attacks.

A preview in February

Iran temporarily shut down parts of the strait in mid-February for what it said was a military drill. Oil prices jumped about 6% in the following days.

The decision was a rare, perhaps unprecedented shutdown of the strait.

In past times of tension and conflict, Iran has at times harassed shipping though the narrows, and during the 1980s’ Iran-Iraq war, both sides attacked tankers and other vessels, using naval mines to completely shut down traffic at points. But Iran has not carried out repeated threats to close the waterway altogether since the 1980s, even during last year’s 12-day war when Israel and the U.S. bombarded Iran’s key nuclear and military sites.

Anderson reported from New York.