Treasury Secretary Scott Bessent telegraphed on Sunday the most expansive American sanctions campaign against Iran in a decade, promising details Monday of measures he described as “the toughest sanctions in the history of economic isolation on a country.” The formal announcement follows a week of escalating pre-announcement language: Bessent told CNBC that Washington was telling third countries “you are either with us or against us,” warned that “any nation that serves as a financial artery of a withering regime should expect to share in its isolation,” and posted on X Sunday evening that “at dawn begins an economic D-Day.” The ceasefire process that had been running in parallel — a 60-day window to reach a formal truce — missed its deadline without a deal, removing the last diplomatic constraint on escalation.
What secondary sanctions actually mean
The structure of what Bessent has described, before the Monday details land, is recognisably that of a secondary sanctions campaign: not additional designations against Iranian entities, but pressure applied to the third-country intermediaries — Chinese refineries, Indian energy firms, Turkish brokers, UAE financial institutions — that have kept Iranian oil flowing and Iranian revenues circulating since the collapse of the JCPOA. The US has already sanctioned a number of Chinese “teapot refineries,” the small independent processors that absorb a significant share of Iranian crude at discount. What Bessent’s language suggests is different in scope: the targeting of the major Chinese banks that finance this trade, which Washington has until now deliberately avoided in order not to trigger a systemic confrontation with Beijing’s financial sector. Whether Monday’s announcement actually crosses that line is the operative question.
Secondary sanctions work by presenting foreign entities with a binary: transact with the designated party, or retain access to the US financial system and dollar-settlement infrastructure. The mechanism has a real track record. The 2012 Iran sanctions campaign — which included secondary sanctions on foreign banks processing Iranian oil payments — contributed materially to a roughly 50 percent drop in Iranian oil exports between 2011 and 2013 and a severe contraction of the rial. That episode, however, operated under conditions that no longer fully obtain. In 2012, dollar-settlement dominance was near-total; SWIFT’s membership included virtually every significant financial institution; and China’s cross-border payment infrastructure (CIPS) was nascent. By 2026, CIPS processes significant volumes of yuan-denominated transactions, a number of bilateral trade relationships have shifted to non-dollar settlement, and Iran has had over a decade to build routing workarounds through intermediary jurisdictions including Iraq, Oman, and the UAE.
Who the real targets are
The Russia sanctions experience after February 2022 is instructive in the other direction. Secondary sanctions pressure on Russian energy exports produced a partial rerouting — Indian and Chinese purchases of Russian crude at steep discounts substituted for European buyers — but did not collapse Russia’s export revenues, which recovered substantially by late 2022 as global energy prices remained elevated. The enforcement gap was structural: Washington was unwilling to escalate to the point of sanctioning Indian state-owned refiners or Chinese national oil companies, because the political cost of a direct confrontation with either government exceeded the sanctions benefit. Bessent’s “you are either with us or against us” framing is maximally explicit about the binary on offer. Whether it reflects a genuine willingness to sanction ICBC or SBI — the major banks that underpin Chinese and Indian dollar access — or is itself pressure calibrated to stop short of that threshold is assessed as unknown from the pre-announcement statements alone.
Iran’s response to the advance announcements has been to contest the legal framework rather than the economic threat. Tehran’s foreign ministry described the secondary sanctions doctrine as an assertion of “extraterritorial sovereignty” — a designation that carries weight with a number of US partners who have themselves been subjects of secondary sanctions exposure. The EU’s 2018 blocking statute was an explicit counter to secondary sanctions reimposition after the Trump administration’s first-term JCPOA withdrawal; European banks and companies exited Iranian business not because they assessed the sanctions legitimate but because the cost of non-compliance was too high. If Monday’s announcement targets major Chinese banks rather than only smaller intermediaries, Beijing’s response will determine whether this round follows the 2012 or the post-2022 pattern.
The enforcement question
The escalation architecture visible in Bessent’s language has one clear structural function: to raise the cost of continued Iranian oil exports to the point where the secondary-sanctions threat becomes credible as a constraint on third-country behaviour, rather than a cost of doing business. Whether the mechanism actually constrains Chinese bank behaviour depends on factors outside Treasury’s direct control — the state of US-China relations at the moment of enforcement, the availability of yuan-routing alternatives, and the political will in Washington to follow through against systemically important institutions. The “collapse the regime” language Bessent used on August 20 is maximally maximalist framing; the actual enforcement posture will be visible in the designations themselves, which arrive Monday.
Ledger predictions
Assessed — moderate confidence: China will not materially reduce Iranian oil purchases within 90 days of the Monday announcement, regardless of its scope, because the domestic refinery economics and strategic reserve incentive outweigh the secondary sanctions threat at current enforcement levels. Resolution date: 24 November 2026.
Assessed — low confidence: The Monday announcement will include designation of at least one major Chinese financial institution (ICBC, Bank of China, or China CITIC Bank) as a signal of escalatory intent. If it does not, the “toughest in history” characterisation will be assessed by counterparties as bluff, reducing deterrent value. Resolution date: 26 August 2026.