The United States has launched a sweeping new sanctions campaign against Tehran, yet its reluctance to directly confront major Chinese banks and companies reveals the limits of economic pressure when Iran’s largest oil customer is also one of Washington’s most important strategic rivals.

The United States has opened a new and potentially far-reaching phase of its economic campaign against Iran, imposing sanctions on dozens of entities linked to Tehran’s oil trade, military procurement and financial networks while warning foreign governments and businesses that continued dealings with the Islamic Republic could carry severe consequences.

But the most consequential player in Iran’s economic survival remains largely untouched.

China, which buys the overwhelming majority of Iranian crude reaching international markets, was conspicuously absent from the most punitive elements of the latest measures. No major Chinese bank was directly targeted in the initial package, despite Beijing’s central role in sustaining an oil trade that has allowed Tehran to withstand years of Western sanctions.

The contrast exposes the central dilemma in Washington’s Iran strategy: economically isolating Tehran in a meaningful way may ultimately require confronting China, but doing so risks turning sanctions policy into a much broader financial and geopolitical conflict.

On Monday, Treasury Secretary Scott Bessent announced the opening phase of what the administration has called “Operation Economic Outcast,” blacklisting roughly 60 individuals, companies and vessels connected to Iranian oil revenues, weapons programmes, cyber operations and sanctions-evasion networks. The administration also signalled that additional restrictions could eventually target areas including shipping, aviation, digital assets, technology and precious metals.

Bessent framed the effort as an attempt to force governments and companies around the world to make a choice: continue doing business with Iran or preserve their access to the dollar-based international financial system.

That threat matters because the reach of American financial sanctions extends far beyond U.S. borders. Global banks and multinational companies remain heavily dependent on dollar transactions, correspondent banking relationships and access to American markets. A credible threat of secondary sanctions can therefore persuade foreign businesses to abandon Iran even when their own governments oppose Washington’s policy.

Yet applying that principle aggressively to China is considerably more complicated.

China is estimated to purchase around 80% or more of Iran’s exported oil, with some assessments placing its share even higher during periods when other buyers have withdrawn. Much of the trade is handled through independent Chinese refiners, often called “teapots,” and supported by shipping arrangements, intermediaries and financial structures designed to reduce exposure to U.S. sanctions.

Before the most recent disruption to Iranian exports, discounted Iranian crude had become an attractive source of supply for Chinese refiners. For Tehran, those purchases supplied one of the government’s most important remaining streams of foreign revenue.

The relationship has made China less a peripheral sanctions-evasion problem than the central economic variable in Washington’s Iran policy.

The United States has previously sanctioned Chinese and Hong Kong entities connected to Iranian weapons procurement, aviation and clandestine finance. Treasury measures in June and July, for example, targeted China-linked individuals and companies accused of supporting Iranian military procurement and Mahan Air.

But targeting relatively small trading companies is very different from sanctioning a major Chinese commercial bank, large state-owned enterprise or strategically important port.

Such a step could have consequences across global markets.

China is deeply integrated into international trade and finance, and its largest banks process enormous volumes of cross-border transactions. Attempting to cut a major institution off from the dollar system could disrupt trade financing, commodity markets and corporate payments far beyond Iran.

Asked why Washington had not immediately escalated against major financial institutions involved in Iran-related commerce, Bessent pointed directly to that risk, asking why the United States would want to destabilise the global financial system.

The administration’s restraint also comes at a sensitive moment in U.S.-China relations.

President Donald Trump and Chinese President Xi Jinping are expected to meet in September, and Washington appears reluctant to allow the Iran campaign to overwhelm wider negotiations involving trade, tariffs and strategic competition. Analysts have therefore interpreted the decision not to sanction major Chinese banks as an effort to preserve leverage over Beijing rather than exhaust it immediately.

That strategy could still put considerable pressure on Iran.

Iranian oil exports have already fallen sharply. Reuters reported that shipments dropped to approximately 534,000 barrels a day in August, compared with an average of roughly 1.4 million barrels a day during 2025. Iranian crude available to Chinese buyers has become scarcer, while some refiners have begun seeking replacement barrels from countries including Brazil and Iraq.

Those figures suggest that Washington does not necessarily need to eliminate Chinese purchases completely to inflict economic damage.

Shipping restrictions, enforcement against intermediaries and pressure on smaller Chinese refineries can increase transaction costs, reduce available buyers and force Iran to offer additional incentives or accept more complex payment structures.

But the durability of that pressure remains uncertain.

Beijing has rejected unilateral U.S. sanctions and warned that it will defend what it considers legitimate economic relations with Tehran. Chinese officials have consistently argued that sanctions cannot resolve the underlying dispute and have opposed Washington’s use of secondary measures against companies operating outside the United States.

Iran, meanwhile, has responded defiantly to the latest package, promising retaliation and expressing confidence that major economic partners will resist U.S. demands.

The strategic question is therefore whether Washington’s threat is credible if the largest buyer of Iranian oil believes the United States will stop short of imposing sanctions powerful enough to threaten major Chinese interests.

Some energy analysts argue that only direct pressure on large Chinese banks, state-owned enterprises and important ports would fundamentally alter the Iran-China trade relationship. Without those measures, Tehran may continue finding ways to monetise at least part of its oil production, even under severe restrictions.

Others believe Washington does not need to trigger a financial confrontation with Beijing.

If Chinese companies increasingly view Iranian transactions as commercially risky, expensive or politically inconvenient, trade could decline without the United States ever sanctioning China’s largest financial institutions. The administration may therefore be attempting to create uncertainty around future enforcement while preserving the option of escalation.

That ambiguity itself is a form of pressure.

For Chinese banks and refiners, the crucial calculation is no longer simply whether they are currently sanctioned. It is whether continuing to process Iranian transactions could expose them to sanctions later.

For Iran, however, the stakes are much higher.

Oil revenue remains essential to government finances, foreign exchange and the broader economy. Any sustained reduction in exports would intensify pressure on Tehran at a time when it is already facing the cumulative impact of conflict, financial isolation and restricted access to international markets.

The latest U.S. campaign therefore represents a substantial escalation — but also illustrates the practical limits of sanctions against a country supported by a major economic power.

Washington can target tankers, brokers, front companies and smaller refiners. It can threaten governments with exclusion from the dollar system and progressively raise the cost of trading with Iran.

What it has not yet demonstrated is a willingness to impose those same costs on China’s most important institutions.

And until that line is crossed — or Beijing voluntarily reduces its economic support — China will remain the central vulnerability in America’s attempt to economically isolate Tehran.