What are Trump's options as US eyes 'never been seen' sanctions on Iran?

US President Donald Trump has vowed to hit Iran hard economically, after treasury secretary Scott Bessent said that Washington would impose measures on Tehran that have "never been seen" as soon as next week.

The United States, ‌the United Nations and the European Union have applied sanctions, implemented trade embargoes and frozen Iranian assets since the late 1970s.

Since the US and Israel launched the war on Iran in February, Washington has levied additional maritime, energy and financial sanctions and started a naval blockade.

Iran — which has withstood decades of punishing sanctions — has denounced US plans to announce new sanctions and on Sunday warned countries against participating in the United States' "economic war" against the country.

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Washington has pushed its allies to jump aboard Trump's new campaign to isolate the Iranian economy, as the US president's unpopular war drags toward the six-month mark.

"We declare to all countries ... do not join the economic war waged by the United States," said Mohsen Rezai, the head of Iran's supreme national security council, on Iranian television.

"Any country participating in the imposition of economic restrictions against us is considered an enemy."

Data from the US treasury department's Office of Foreign Assets Control (OFAC) shows the agency has imposed sanctions on more than 1,000 people, vessels and aircraft since Trump began his second term.

Recent measures have targeted Iran's shadow oil fleet; shipping insurers; entities and people enabling Iran's acquisition of weapons; and digital exchanges, freezing an estimated US$500 billion ($697 billion) in Iran-linked cryptocurrency.

Oil shipments are at a virtual standstill in the Strait of Hormuz, with Tehran threatening to strike any unauthorised oil tankers that try to transit the vital waterway.

Experts say the Trump administration can try the following options to put more pressure on Iran:

Chinese independent refineries known as "teapots" account for a quarter of Chinese refinery capacity. They operate with narrow and sometimes negative profit margins.

China buys more than 80 per cent of Iran's shipped oil, according to 2025 data from analytics firm Kpler. Independent refiners absorb much of this trade, exposing them to so-called secondary measures that penalise entities helping a primary sanctions target.