Comex copper stocks hit record high after US arbitrage reopens

Copper inventories on the US Comex exchange have climbed to a record high, data from the bourse showed on Wednesday, as traders take advantage of the renewed price arbitrage to ship metal to the United States.

Total copper stocks in Comex warehouses rose by 0.5% to 603,745 short tons (547,708 metric tons) on Tuesday from the day before, the data showed, beating the previous peak of 601,716 short tons on March 2.

Copper prices on the Comex began to trade higher than those on the London Metal Exchange again earlier this month, incentivizing shipments to Comex warehouses once more after a slight dip in stocks in March.

The US arbitrage was open for much of 2025, drawing in hundreds of thousands of tons of copper on expectations the metal could be hit with a US tariff; refined copper was ultimately given an exemption but remains under review.

More copper will flow to the US until at least July, when a decision is expected on whether to impose tariffs, the global head of metals at Mercuria said on Wednesday.

More than two-thirds, or 414,984 short tons, of the Comex copper stocks are in the key storage hub of New Orleans.

(By Tom Daly; Editing by Deepa Babington)