Copper Rally Tests Supply Tightness as Tariff Positioning Pushes the Comex Premium to $600

• Comex copper climbed 3.3% to $6.55 a pound ($14,440 a tonne), leaving it within 2% of June's record, while LME three-month copper gained 1.7% to $13,851 a tonne.
• Shanghai Futures Exchange deliverable stocks have collapsed 82% since early May, pushing the Yangshan import premium from $20 in January to $103 a tonne as tighter inventories increased demand for imported copper.
• New York's premium over London widened to nearly $600 a tonne, more than double Monday's gap, as traders priced in a pending US tariff on refined copper that could raise domestic metal costs.
• Higher copper prices more than offset weaker production, lifting quarterly mining earnings despite a 3.7% decline in output.
• The pending Commerce Department tariff ruling will determine whether the New York-London copper premium holds, with a delay likely to narrow the current $600-a-tonne gap.

US Tariff Expectations Widen the Comex-LME Premium, Supporting Higher Copper Prices

Comex copper jumped 3.3% to $6.55 a pound ($14,440 a tonne), within 2% of June's record, while LME three-month copper gained 1.7% to $13,851 a tonne, its highest level since June 15.

The New York premium over London widened to nearly $600 a tonne, more than double Monday's gap. The move reflects the market pricing in a pending US tariff on refined copper rather than a global supply shortfall. The premium signals higher expected import costs for refined copper into the US, widening the price gap with other markets.

Shanghai Inventories Fall 82% as Smelter Disruptions Tighten Copper Supply, Supporting Prices

Deliverable copper stocks on the Shanghai Futures Exchange have collapsed 82% since early May, while LME inventories have fallen 28%, with more than half already queued for withdrawal. At the same time, smelter outages have tightened refined copper supply, leaving 16% of global capacity inactive in the second quarter and Chile's idle capacity at 25.4%, the highest since 2019.

Record-low treatment charges are forcing permanent smelter closures, including Japan's 354,000-tonne-a-year Onahama smelter, which will stop processing concentrate in early 2027. Meanwhile, the White House is weighing phased US copper tariffs of 15% from January 2027 and 30% in 2028 after the Commerce Department's review concluded, driving Comex copper inventories above a record 630,000 tonnes as traders position ahead of potential import duties.

Physical Tightness & Commerce Department Ruling Will Determine Whether Copper Prices Hold

The LME cash-to-three-month spread has narrowed toward backwardation, signaling sustained physical tightness rather than a one-day price move. ING commodities strategist Ewa Manthey said copper is being driven higher by a tightening Chinese market but warned the rally will need continued evidence of physical tightness to extend.

White House confirmation of phased tariffs of 15% in 2027 and 30% in 2028 would likely keep the Comex-LME premium near current levels through the January 2027 start date. A delay could unwind tariff-driven positioning, narrowing the premium and reducing the incentive to hold the record 630,000-tonne Comex stockpile.

Higher Copper Prices Lift Producer Earnings, Encouraging New Copper Supply

Grupo Mexico's Q2 results showed that higher copper prices more than offset weaker production, lifting net profit 79% to $2.20 billion despite a 3.7% decline in output. The market rewarded the same dynamic across the sector, sending Freeport-McMoRan up 6.3%, Southern Copper 6.5%, and Teck Resources 3.7%.

Grupo Mexico is reinvesting into future copper supply rather than preserving its windfall, raising $1.25 billion in bonds for Peru's Tía María project, now 42% complete and scheduled to begin operating in the second half of 2026.

The key near-term risk for copper equities is the Commerce Department's tariff decision. Because the Comex-LME premium has been driven by tariff expectations rather than confirmed trade flows, a delayed or less restrictive ruling could quickly narrow the spread. Renewed Chinese destocking would add further pressure by weakening physical demand and reducing support for copper prices.

$600 Comex-LME Premium Narrows if Tariffs Are Delayed, Testing Copper Prices

The current rally depends on the nearly $600-a-tonne Comex-LME premium, which more than doubled by July 21 as tariff expectations pulled copper into the US market. While that spread holds, US-facing refiners and Comex inventories remain better positioned than London-facing exposure.

The Commerce Department's ruling on phased tariffs of 15% from January 2027 and 30% in 2028 is the key catalyst for the current rally. A delay or rejection could unwind tariff-driven positioning, narrowing the New York premium and reducing the incentive to hold the record 630,000-tonne Comex stockpile.

The key indicators are the still-unscheduled Commerce Department tariff ruling, the LME cash-to-three-month spread, and Shanghai Futures Exchange inventories. A deeper move into backwardation or a further decline from current inventory levels would reinforce the tightening thesis, while stabilization in either would suggest physical tightness is easing.