Comex Copper Stocks Jump 750% as Incentive to Ship to U.S. Shrinks
Key Facts
Copper inventories on Comex have risen about 750% since the end of February 2025 to more than 714,000 tonnes, according to a Reuters report published on October 14, 2026, as supplies concentrate in the United States and availability tightens elsewhere. Reuters estimated that U.S. warehouses approved by the exchange held about 70% of visible global copper inventories. It linked this concentration to reduced metal availability in markets outside the United States, despite a global surplus, making the location of inventories a factor affecting supplies to buyers. Looking beyond exchange inventories, Macquarie estimated total copper stored in the United States at about 1.6 million tonnes, Reuters reported in the same article. Macquarie's estimate includes metal held both on and off exchanges, while the increase recorded since the end of February relates to Comex inventories.
As metal accumulated in the United States, the price gap encouraging further copper shipments there narrowed, according to Reuters. The arbitrage spread in favor of Comex stood at about $310 per tonne in the agency's October 14 report, which linked its contraction to a weaker incentive to move additional supplies to the U.S. market. By comparison, the spread exceeded $3,000 per tonne at its record peak in July 2025, according to Reuters. On the global supply balance, the International Copper Study Group forecast a refined copper surplus of about 104,000 tonnes in 2026, according to Kedia Advisory via Investing.com. The group projected that the surplus would widen to 368,000 tonnes in 2027, alongside the continued imbalance in inventory distribution between the United States and other markets described by Reuters.
Copper supplies face production constraints that S&P Global linked to mine disruptions, declining ore grades and long project development lead times. These constraints affect existing mining operations through disruptions and ore quality, as well as projects that take a long time to develop. On the demand side, the firm pointed to support from electricity, power grids and artificial intelligence infrastructure. Against the U.S. tariff backdrop, a presidential proclamation set June 30, 2026 as the deadline for the commerce secretary to provide an update on the domestic market and refining capacity, enabling the president to assess proposed tariffs on refined copper. For goods deposited in bonded warehouses, the U.S. International Trade Commission states that "duties become payable when goods are withdrawn from the bonded warehouse for domestic consumption."
On upcoming supply developments, Teck said it had received strike notice at its Highland Valley Copper operations, allowing the union to begin action as early as October 24, 2026. The company specified 8:00 a.m. Pacific time as the earliest permitted start of a strike and said operations were continuing, with contingency plans in place to maintain safety and environmental management during the labor action. Further out on the tariff horizon, the U.S. presidential proclamation included a proposed path to impose a 15% tariff on refined copper starting January 1, 2027. The proposal calls for raising the tariff to 30% starting January 1, 2028, with the president to decide whether its imposition is warranted. As of the Reuters report dated October 14, 2026, no decision on the proposed tariffs had been announced, and implementation of the rates and dates set out in the proposed path remained subject to a presidential decision.