How China can help Iran block key shipping route

Loading

An Iranian blockade of the Strait of Hormuz would choke access to neutral gulf ports without targeting contraband or enemy vessels – neither the United States nor Israel is based inside the gulf, Bahrain’s US naval facility notwithstanding. Because it would indiscriminately impede neutral trade, such a move would fall outside the legal limits of naval blockade, despite the Iranian Parliament’s reported approval.

Even if an outright blockade breached international law, Tehran could still attempt to close the strait. Its conventional navy is ageing and limited, but the Islamic Revolutionary Guard Corps Navy fields swarms of fast-attack craft, anti-ship missiles, drones and mines – an asymmetric mix designed for narrow-water choke-points. Iran would not even have to act decisively: a simple claim that it had laid mines could divert commercial traffic until US-led forces proved the channel clear, a process that could take weeks.

Despite years of rhetoric, Tehran is unlikely to close the strait. Its strategic partnership with Beijing is a brake: China is the world’s largest crude importer, and roughly half of its oil arrives via gulf producers transiting the strait. Crippling that flow would undercut a key supporter and damage Iran’s own diplomatic gains with Beijing.

China is hardly alone in its dependence on Strait of Hormuz oil. A closure would jolt the global economy and bite Australia in particular. Despite the 8000-kilometre distance, most of Australia’s crude arrives via this chokepoint, and the nation imports about 91 per cent of its fuel.

Loading

Most of Australia’s petrol, diesel and jet fuel arrives as finished product from refineries in Singapore, South Korea and Japan, but those refineries source much of their crude from the Middle East via the Strait of Hormuz. Any prolonged disruption there would therefore ripple straight down Australia’s supply chain. The risk is magnified by Canberra’s chronic shortfall against the International Energy Agency’s 90-day stockpile obligation: as of March 2025, Australia held barely 56 days of fuel in reserve.

Australia’s 1990-2020 naval deployment to the Middle East was never mere alliance diplomacy; it safeguarded the long sea lines that bring fuel to Australia. That dependence remains, yet decades of under-investment leave the Royal Australian Navy with only 10 surface combatants until the 2030s – several in refit – hardly able to assist in breaking an Iranian blockade today if Washington came calling.

Despite the Iranian parliament’s vote to “blockade” the Strait of Hormuz, Tehran is unlikely to follow through. Shutting the waterway would penalise neutral gulf ports and anger China – its most important economic partner and a veto-wielding UN Security Council member. Even so, experience shows any escalation will spill into the maritime domain. For Australia, the message is clear: rebuild strategic fuel stocks to meet International Energy Agency obligations and strengthen supply-chain resilience; and, as an island nation reliant on vulnerable sea-lines of communication, invest now in a navy capable of keeping them open.

Jennifer Parker is a defence and national security expert associate at the ANU’s National Security College. She has served for more than 20 years as a warfare officer in the Royal Australian Navy.