First, it was the Panama Canal, then came the Strait of Hormuz. What could be next?

America’s actions in the two major shipping channels have grabbed headlines, and global attention is shifting to the strategic importance and potential risks of other critical trade waterways.

Some of the chokepoints were examined in a US Federal Maritime Commission (FMC) investigation in March last year of unfavourable shipping conditions, signalling America’s heightened focus on international routes and offering a glimpse of what else might be on its radar.

Strait of Malacca and Singapore Strait

Connecting the Indian and Pacific oceans, the two straits form a continuous corridor that is the world’s busiest route for crude oil and petroleum liquids in terms of barrels per day.

The roughly 800km (497-mile) funnel – under two nautical miles at its tightest point – carries nearly 40 per cent of global trade and about one-third of the world’s seaborne oil and other liquid cargo.

This makes it a critical maritime bottleneck linking the Middle East and Europe with the Asia-Pacific region.

China, as the world’s second-largest economy, relies heavily on the narrow channel for its oil imports, leading to the notion of a “Malacca dilemma”.

The two straits are jointly managed by Malaysia, Singapore and Indonesia, and both were included in the FMC examination.

The US-Indonesia Major Defence Cooperation Partnership signed last week has raised debate over that deal’s possible impact on the corridor.

Ali Akbar Velayati, a senior adviser to Iran’s supreme leader, wrote on social media on Sunday that the Strait of Malacca’s security was now in the hands of “our strategic partners”.

Turkish straits

Comprising the Bosphorus, Sea of Marmara and the Dardanelles straits, the 300km system is located between Europe and Asia. It offers the only natural maritime outlet from the Black Sea to the Mediterranean Sea.

Turkey holds control over foreign warships’ transit in the straits, which are governed by the Montreux Convention of 1936. The waterways see a significant volume of grain exports, particularly from Ukraine, and the system also serves as a crucial link in the world’s fertiliser supply chain.

Following Russia’s invasion of Ukraine in 2022, the Black Sea Grain Initiative signed in July that year by Russia, Turkey, Ukraine and the United Nations underscored the route’s vital role in global food security as well as the geopolitical challenges it could be exposed to.

Suez Canal

Linking the Mediterranean Sea to the Red Sea, Egypt’s man-made sea-level waterway has served as the shortest maritime route between Europe and Asia since 1869, eliminating the need to sail around Africa.

More than one-tenth of worldwide trade passes through the canal and about 30 per cent of global container traffic.

In a note about its investigation a year ago, the FMC said: “Events such as the 2021 Ever Given blockage highlighted the canal’s vulnerabilities, causing massive trade disruptions.”

The note referred to the massive container ship that ran aground, blocking the canal for six days and causing a major backlog of waiting vessels.

Holding up billions of dollars in daily cargo, the incident laid bare global trade’s heavy dependence on the narrow channel.

Bab el-Mandeb Strait

Forming the southern maritime gateway to the Suez Canal, the strait is also known as the Gate of Tears and is located between Yemen and Djibouti. It connects the Red Sea with the Gulf of Aden and the wider Indian Ocean.

Since November 2023, the Iran-backed Houthi rebels have launched drone and missile attacks against commercial ships in the Red Sea. These strikes are an attempt to pressure Israel following the outbreak of the Israel-Gaza war.

The attacks in the Bab-el-Mandeb Strait have forced major shipping companies to divert vessels around Africa’s Cape of Good Hope, raising costs.

Tehran recently warned that its allies would close the Bab el-Mandeb if the US was to blockade Iran’s ports.

If the strait, whose narrowest point measures about 26 to 30km, was shut along with the Strait of Hormuz, a quarter of the world’s energy supply would be blocked.

Strait of Gibraltar

The strait is the only natural entrance to the Mediterranean from the Atlantic. It is a high-traffic highway for consumer goods destined for southern Europe and North Africa, measuring about 14km wide at its narrowest point.

Named after the British overseas territory of Gibraltar, ceded under the 1713 Treaty of Utrecht, the waterway borders both Spain and Morocco at the southern tip of the Iberian peninsula.

Although Madrid continues to claim sovereignty over Gibraltar, London maintains legal control over the territory.

Morocco, which sits on the strait’s southern coast, operates the Tanger-Med port, which has become the largest container port in Africa and the Mediterranean.

The FMC note said that “geopolitical tensions between Spain [and] Morocco and issues surrounding the status of Gibraltar, along with piracy and smuggling, contribute to security concerns and potential disruptions in the region”.

Taiwan Strait

Although not included in the FMC examination, this body of water between the island of Taiwan and the Asian continent carries about half of the world’s active container fleet and more than one-fifth of global seaborne trade.

Stretching roughly 400km in length and at least 130km in width, it also serves as a major shipping route for the global semiconductor supply chain, particularly given Taiwan’s roughly 90 per cent share of advanced chip production.

In recent years, rising cross-strait tensions have led the international community to focus more closely on the maritime corridor’s security.

Beijing sees Taiwan as part of China to be reunited by force if necessary.

Most countries, including the United States, do not recognise Taiwan as an independent state, but Washington is opposed to any attempt to take the self-ruled island by force and is committed to supplying it with weapons.

Luzon Strait

The roughly 250km-wide channel sits between the island of Taiwan and Luzon, the northern portion of the Philippine archipelago.

Lying just south of the Taiwan Strait, it is less busy but still an important shipping lane for trade between Southeast Asia and the Americas. It also hosts a dense network of undersea fibre-optic cables essential to global internet connectivity.

Often seen as an alternative route to the Taiwan Strait, the Luzon Strait links the wider Pacific Ocean with the South China Sea, which handles over 40 per cent of propane flows and more than one-fifth of automotive trade.

As competing claimants, Beijing and Manila have seen tensions over the South China Sea flare in recent years.

Arctic Sea route and Bering Strait

A study published in September last year by scholars from Peking University’s Shenzhen Graduate School predicted that, by 2100, the Arctic could support year-round navigation for all major vessel types. This would allow routes across the ocean to handle a portion of global shipping traffic that would surpass the Suez Canal and the Panama Canal in volume, the study said.

According to the study, the opening of the Arctic Sea route “will reshape global maritime trade, positioning the Bering Strait as a critical chokepoint”.

Connecting the Arctic Ocean to the north with the Pacific to the south, the strait is about 80km wide at its narrowest point and separates Russia to the west from the US state of Alaska to the east.

In its note, the FMC said the northern sea passage was “emerging as a critical maritime chokepoint as new shipping routes open, a development that could reshape global trade patterns”.