On Monday, Yemen's Houthis announced a blockade of Saudi Arabia, marking a major escalation that could ratchet up pressure on global oil markets at a time when U.S. and global oil stockpiles are dangerously depleted.

A Houthi blockade could also subject Saudi Arabia to the same broad-based economic warfare the U.S. has waged by blockading Iran. The Red Sea, bordered by Yemen to the southeast, has emerged not only as a crucial outlet for oil rerouted from the Strait of Hormuz to global markets, but also as an important conduit for grain and other crucial imports to Saudi Arabia and other GCC countries.

Thus the blockade, if enacted, could pressure President Donald Trump to scale back his strikes on Iran in two major ways: by threatening economic calamity through skyrocketing oil prices, and by pressuring the Saudis to disallow the use of their bases and airspace for attacks against Iran. Recall that Saudi disapproval prompted Trump to suspend Project Freedom, the U.S. initiative to guide shipping through the Strait of Hormuz in early May, barely two days after it began.

The Houthis' leverage is substantial. Houthi attacks could jeopardize global access to the roughly 4.6 million barrels per day that Saudi Arabia currently exports through the Red Sea port of Yanbu. The Houthis could suppress these exports by targeting Yanbu directly or by attacking shipping through the Bab-el-Mandeb waterway that connects the Red Sea to the Gulf of Aden and greater Indian Ocean.

Yanbu, located on the northern end of the Red Sea, is more difficult for the Houthis to reach because of its distance from Yemen and the presence of Saudi air defenses capable of intercepting Houthi attacks. But Yanbu is within the demonstrated range of Houthi missiles and drones, which have hit targets in Israel, several hundred miles to the north. And the Houthis might not have to completely disable Yanbu to effectively suppress commercial traffic flowing through it.

Attacking shipping through the Bab-el-Mandeb is much easier for the Houthis to accomplish because of its proximity to Houthi strongholds in Yemen. From late November 2023 through mid-2024, sustained Houthi anti-ship missile and drone attacks, conducted in protest of Israel's war in Gaza, drove Bab el-Mandeb vessel transits down by 60%. Choking the Bab-el-Mandeb, even if Yanbu remains operational, could significantly constrain daily oil throughput to world markets. Instead of using the Bab-el-Mandeb, oil destined for Asia would have to reroute through the Suez Canal to the Mediterranean Sea and onward around the Cape of Good Hope – adding roughly 2-3 weeks of transit time and increasing fuel and insurance costs.

The constrained capacity of the Suez Canal represents an additional bottleneck. Unlike the Bab-el-Mandeb, Suez cannot accommodate fully-laden Very Large Crude Carriers (VLCCs), the largest oil tankers that carry up to 2 million barrels. If tanker traffic from Yanbu was forced northward through the Suez Canal, that would necessitate a switch to smaller-capacity Suezmax tankers, which can only hold 1 million barrels. In principle, some Red Sea oil could bypass Suez using the SUMED pipeline across Egypt, but that route is already running at its full nameplate capacity of 2.5 million barrels per day.