Iran's oil shipments to Asia have nearly ceased, pushing cargo prices to multi-year highs even before the US announces new isolation measures. China's private refiners, traditionally the largest buyers of Iranian crude, face severe supply shortages. Prices have shifted from a discount to a premium of approximately $4 a barrel over global benchmarks, according to traders involved in private negotiations.

The market tightening comes as Treasury Secretary Scott Bessent prepares to unveil an economic isolation plan targeting Tehran and its trading partners. The supply disruption highlights the immediate market impact of geopolitical pressure on Iranian oil flows.