Features | Economy | Southeast Asia

The Strait of Malacca: The Indo-Pacific’s Most Critical Chokepoint?

The vulnerabilities of Hormuz and Malacca are fundamentally different – but a closure of the Strait of Malacca would be far worse.

Large numbers of ships waiting at anchor off the coast of Singapore in the Malacca Strait.

Iran’s blockade of the Strait of Hormuz in response to U.S. and Israeli strikes has once again highlighted one of the world’s most persistent strategic vulnerabilities. Around 80 percent of global trade by volume is transported by sea, and a remarkably large share of that traffic passes through a handful of narrow maritime chokepoints. Roughly one-quarter of all seaborne oil trade and about one-fifth of global liquefied natural gas (LNG) shipments normally transit the Strait of Hormuz; farther east, the Strait of Malacca, which links the Indian and Pacific Oceans, handles more than one-fifth of global maritime traffic, including an even greater share of energy supplies, industrial components and manufactured goods.

The Red Sea crisis in 2023, triggered by Houthi attacks on commercial shipping transiting the Bab el-Mandeb Strait, had already exposed the fragility of these maritime corridors. More recently, Iran’s use of Hormuz as a geopolitical lever demonstrated how a single actor can exploit geography to exert strategic pressure during a conflict. Together, these episodes have underscored two enduring vulnerabilities: the ability of states to weaponize their geographic position, and the difficulty the international community faces in preventing both state and non-state actors from disrupting essential trade routes.

Indeed, even without a closure, attacks or threats against key maritime corridors can drive up insurance premiums, force vessels onto longer and more expensive routes, and significantly increase transportation costs. In an interconnected global economy, a single chokepoint can quickly become a source of worldwide economic disruption.

Yet the vulnerabilities of Hormuz and Malacca are fundamentally different. Hormuz is primarily exposed to geopolitical coercion: the possibility that a coastal state could deliberately restrict navigation to achieve political objectives. Malacca, by contrast, owes much of its strategic importance to geography itself. Any prolonged disruption would not simply affect a regional market but would reverberate across the entire trading system connecting the Indian and Pacific Oceans. For Asian economies, which rely on the strait for most of their energy imports and a substantial share of their raw materials, the economic consequences would be immediate and severe.

Stretching roughly 900 kilometers between Indonesia’s island of Sumatra and the Malaysian Peninsula, the Strait of Malacca is the shortest maritime route linking Europe, the Middle East, and East Asia. It connects the Indian Ocean with the South China Sea and, ultimately, the Pacific, making it one of the busiest shipping lanes in the world. 

Its geography, however, presents significant operational challenges: the waterway narrows dramatically at the Phillip Channel near Singapore, where it measures less than 3 kilometers across. This narrow passage represents the principal bottleneck of the entire corridor and one of the most congested stretches of water. Its physical characteristics make Malacca vulnerable not only to geopolitical tensions but also to operational risks. Heavy traffic increases the likelihood of collisions, while piracy – although significantly reduced compared to previous decades – continues to pose a security concern. 

From an energy perspective, its importance is even greater: more than one-quarter of global seaborne oil shipments transit Malacca – an even larger share than passes through the Strait of Hormuz. The two waterways are, in fact, deeply interconnected. Much of the crude oil crossing Malacca originates in the Persian Gulf and has already passed through Hormuz before continuing toward the major economies of East Asia, particularly China, Japan, and South Korea.

Unlike the Suez or Panama Canals, Malacca is not an artificial waterway administered by a single authority. Instead, the strait falls under the jurisdiction of Indonesia, Malaysia, and Singapore, which jointly share responsibility for ensuring its security and managing navigation. Its legal regime is governed by the 1982 United Nations Convention on the Law of the Sea (UNCLOS), ratified by all three littoral states. Under the convention, the strait is subject to the principle of transit passage, which guarantees vessels of all nations the right to navigate continuously and expeditiously without coastal states being able to suspend transit, arbitrarily restrict access or impose tolls. 

This legal framework does not make a disruption impossible, but it does make a deliberate closure considerably less likely. Any attempt to block navigation would require one or more littoral states to openly violate their obligations under UNCLOS. Barring a major regional conflict, a politically motivated closure of Malacca therefore remains a relatively unlikely scenario.

Moreover, Malacca is not the only available route between the Indian and Pacific Oceans. Alternative passages, including the Sunda, Lombok, and Makassar Straits, provide possible detours through the Indonesian archipelago. None, however, offers a fully comparable substitute. The Sunda Strait presents significant navigational constraints, while Lombok and Makassar can accommodate larger vessels but require considerably longer voyages, increasing sailing times, fuel consumption, and shipping costs. In other words, alternative routes may reduce the risk of complete maritime paralysis, but they would do little to limit the substantial economic costs of a prolonged disruption in Malacca.

Governing the World’s Busiest Waterway

The stability of the Strait of Malacca ultimately rests on a delicate balance between regional cooperation and great power competition. Malacca’s management is the product of decades of institutionalized cooperation between Indonesia, Malaysia, and Singapore, built around a common objective: keeping one of the world’s most important trade routes open.

For all three countries, freedom of navigation is not simply a legal principle but a vital economic interest. The uninterrupted flow of maritime commerce underpins their prosperity, making cooperation less a political choice than a strategic necessity. This does not mean, however, that the strait is immune from instability. On the contrary, Malacca has increasingly become a space where commercial interests, national security concerns, and geopolitical competition intersect. 

Since the 1970s, Indonesia, Malaysia, and Singapore have progressively strengthened cooperation on maritime security, coordinating naval patrols, counterpiracy operations, and traffic management. The durability of this framework helps explain why, despite its immense strategic importance, Malacca has avoided the kind of prolonged disruptions experienced by other major chokepoints. Geography itself reinforces this cooperative approach. None of the three littoral states exercise exclusive control over the entire strait, nor could any of them secure it independently. 

Yet cooperation should not be mistaken for complete strategic alignment. While all three governments have a strong interest in preserving stability and freedom of navigation, they do not necessarily attach the same strategic value to the strait.

Singapore has perhaps the most to lose from any disruption. The city-state has built much of its economic success on its role as Southeast Asia’s premier logistics and financial hub. Its port – the world’s second busiest container port – serves as the principal transshipment........

© The Diplomat