Copper’s Longest Rally Since 1994 Sits in U.S. Warehouses

LME copper notched a 10th straight weekly gain through September 4, and the benchmark traded at $14,430 a metric ton on September 7, just $97.50 shy of January’s record $14,527.50. Comex warehouses, by then, held a record 695,624 metric tons.

The run is the longest weekly winning streak since 1994. The metal that would normally sit in London to feed that price is instead stacked in the United States, shipped in to beat a refined-copper duty Washington has yet to impose.

Why Copper Is Tight in London and Glutted in the U.S.

Visible copper did not vanish. It changed address. On September 7, cancelled LME warrants, metal already tagged for withdrawal, stood at 51%, more than 121,000 tons lined up to leave the London system, while Comex stocks of 766,795 short tons, or 695,624 metric tons, sat at a record. Shanghai Futures Exchange stocks were 63,000 tons, down 85% from mid-March and the lowest since January 2024.

LME warehouse stocks had already fallen for 42 straight sessions through mid-August, the longest drain since 2014. Cash metal in London paid more than $430 a ton over the three-month contract in the middle of that month, the widest gap since the 2021 squeeze; that premium had cooled to about $74 by September 4, but the metal had not come back.

WHERE THE METAL IS SITTING

U.S. ports took in more than 200,000 metric tons of refined copper in July, the largest monthly haul in IHS Markit shipping data going back to 2014. Morgan Stanley, in a late-July estimate, put tariff-front-running imports since the start of 2026 at about 335,000 metric tons. Comex stocks had been near 80,000 tonnes as recently as February 2025. Combined U.S. holdings, exchange metal plus private port storage, have been put above 1 million tonnes.

Traders Are Front-Running a Duty That Does Not Exist

On July 30, 2025, President Donald Trump signed Proclamation 10962 under Section 232, putting a 50% tariff on semi-finished copper products and copper-intensive derivatives from August 1, 2025. The same order left a hole big enough to drive a ship through: refined cathodes, the form that actually trades on the LME and Comex, were held back for a later call.

Commerce was told to study U.S. refining and come back with an 15 percent tariff starting in 2027, stepping up to 30% on January 1, 2028, if the president judged it warranted. The White House fact sheet that day was blunt about the present tense: cathodes and scrap stay off the tariff list, along with ores, concentrates, mattes and anodes.

That exemption is the pipeline. Import now, store in a Comex shed, and if a 15% levy lands on January 1, 2027, the metal already inside the border is worth more than the metal still on the water. Every extra week without a decision keeps that trade alive. Societe Generale in August priced the chance of the 15% duty arriving on schedule at 14.6%, which is another way of saying the market itself doubts the tax that is moving the ships.

An April 2, 2026 proclamation then applied the existing copper duties to full customs value and reset some rates at 50% and 25%, still without taxing refined cathodes. The original review date came and went.

Grasberg Is Still at Half Speed a Year Later

September 8, 2025, is the other date under this rally. Freeport-McMoRan’s Grasberg Block Cave in Papua, Indonesia, the world’s second-largest copper mine, took an external mud rush from the old open pit through an undetected path into the underground workings. About 800,000 tons of wet material moved. Freeport’s November 18, 2025 update said seven co-workers died in the mud rush.

We mourn the loss of our seven co-workers and grieve with their families, friends and loved ones. Their memories will be forever present as we go forward.

Richard Adkerson, Chairman, and Kathleen Quirk, President and CEO, Freeport-McMoRan November 2025 update

PT Freeport Indonesia declared force majeure on September 24, 2025. Unaffected Big Gossan and Deep MLZ mines restarted in late October. The Block Cave, which holds about half of Grasberg’s copper reserves, did not.

THE YEAR AFTER THE MUD RUSH

1. September 8, 2025: Mud enters the Grasberg Block Cave from the former open pit; seven workers are found deceased on the service level.
2. September 24, 2025: PTFI notifies counterparties of force majeure; 2026 output is flagged about 35% below the old plan.
3. Late October 2025: Big Gossan and Deep MLZ restart; Block Cave cleanup continues.
4. April 23, 2026: Freeport cuts the mid-year recovery target to about 65% of capacity, from 85%, after groundwater made remaining ore wetter.
5. May 8, 2026: PTFI chief executive Tony Wenas says the complex is at around 40% to 50% and full capacity is now aimed at early 2028.

Grasberg produced 1.8 billion pounds of copper in 2024. Through July 2026 the complex was still near half speed, with 65% the target for later in the year. Kathleen Quirk, Freeport’s chief executive, said the engineered fix was understood and that large-scale production could be restored safely. It will not be restored this year.

5.27 Million Tonnes, and Falling Grades

The International Copper Study Group’s first-half 2026 mine tally fell 1.1%, to 11.34 million tonnes from 11.47 million. The losses clustered in three places, and new ramps in Peru and Mongolia did not cover them.

MINE HITS IN THE FIRST HALF

• Chile: Mine output dropped 6.6% as El Teniente, Escondida and Spence lost ground, with concentrate down 8%.
• Indonesia: Concentrate output fell 32% with Grasberg still throttled.
• Congo: Concentrate output fell 34% after the 2025 seismic hit at Kamoa, even as SX-EW cathode rose 8%.

Chile’s copper commission, Cochilco, on August 11 cut the 2026 national forecast to 5.27 million tonnes, a 2.6% decline, with a bounce to 5.55 million tonnes pencilled in for 2027. Codelco, the state miner, produced 564,000 tonnes in the first half, down 11%, and still booked pre-tax profit of $1.97 billion against $429 million a year earlier because the realized copper price jumped 41.5% to 653.2 cents a pound. El Teniente, still working through the July 2025 tunnel collapse, managed 102,900 tonnes in the first five months, down 27.2%, and the Andes Norte expansion meant to replace that rock was halted on seismic risk on August 4, with first production now talked about for 2029.

It’s declining grades at existing operations. It’s tired, very, very old assets.

Evy Hambro, BlackRock

Codelco chairman Bernardo Fontaine told a congressional committee in July that output in the coming years was likely to sit near current levels rather than climb toward the old 1.7 million-tonne goal by 2030. The ore is poorer. The mines are older. Price is doing the work volume used to do.

Congo Banned Concentrate After the Metal Had Already Moved

A June 29 order signed by Mines Minister Louis Kabamba Watum, Foreign Trade Minister Julien Paluku Kahongya and Economy Minister Daniel Mukoko Samba, and published on August 6, said the export of copper and cobalt concentrates is prohibited, with one-year waivers possible in “strategic” cases. Three-month copper in London jumped as much as 1.8% to $14,369.50 a ton on the news, the highest since the January record.

The tonnes behind that spike were thin. In the first quarter of 2026 Congo exported 696,725 tons of copper cathode and only 53,926 tons of concentrate, containing 18,863 tons of copper metal. Most of the country’s copper already leaves as refined metal. Kinshasa has banned concentrate before, in 2013 and 2019, then issued waivers when local smelters could not take the feed. China’s concentrate imports from Congo were already down 31% in the first half. BMI, a Fitch Solutions unit, said the order was unlikely to move global balances in a material way and would add a risk premium while the fine print was read.

The price still jumped, because this market now treats any supply headline as a reason to bid. That reflex is the story more than Congo’s concentrate dockets.

ICSG’s Surplus Versus Citi’s $15,000 Call

In Lisbon on April 23, the International Copper Study Group cut 2026 mine-growth to 1.6% from 2.3%, citing Grasberg, Kamoa, Chile and the DRC, and still 96,000-tonne refined surplus for 2026, flipping an October forecast of a 150,000-tonne deficit. Refined output was seen up only 0.4% as concentrate stays tight, with scrap and SX-EW filling part of the hole. Usage growth was marked down to 1.6%. For 2027 the group’s surplus widens to 377,000 tonnes.

H1 mine output then came in negative, so the April surplus is not a settled fact. It is the official reminder that refined metal and mine metal are not the same thing, and that smelters can keep pouring while pits struggle, if scrap shows up.

THE CALLS ON THE BOARD

Citigroup analyst Tom Mulqueen told clients the bank had turned bullish for the first time in 2026 on tariff ambiguity, slower mine and scrap growth, and demand from power and AI build-out, and flagged a 2027 deficit around 360,000 tonnes. Goldman, in the same week, assumed Washington would keep delaying a refined duty and still lifted its year-end target. Anglo American’s Ruben Fernandes put the mood in one line: everyone is investing in copper, everyone likes copper. Supply, he said, will come. The question is how quickly.

If Washington Never Taxes the Cathodes

The Commerce secretary’s updated copper-market assessment by June 30 was the input for a presidential call on that 15% levy. By early September the White House had not made it. Refined metal is still free to enter. Semi-finished product is not. Traders have spent a year acting as if the free window will slam shut, which is why London is short of nearby metal and New York is not.

If the duty arrives on January 1, 2027, the metal already in Comex sheds is a stockpile behind a wall, and LME tightness can last. If it is delayed again, narrowed, or never applied to cathodes, some of that 695,624 metric tons can head back toward the rest of the world, and the premium London has been paying is the first thing that gives. The delay is doing more daily work than the tax, because the delay is what keeps the ships pointed at U.S. docks.

Mine supply is genuinely weaker than it was a year ago, Grasberg is still at half speed, and Chile has cut 2026 twice. That is the floor under the price. The ceiling is a U.S. warehouse complex that has already taken the metal everyone else is bidding for. On September 7, with LME copper at $14,430 a ton, those two facts sat in the same market and did not cancel each other out.

Disclaimer: This article is news reporting and analysis of copper prices, mine output and trade policy, and it is for information only. It is not investment advice, a recommendation to buy or sell copper, copper futures, mining shares or any related instrument, and it is not legal advice on tariffs or customs. Readers should consult a licensed financial adviser and, where trade exposure is involved, a qualified customs or trade counsel before acting. Figures, warehouse stocks, forecasts and the status of the Section 232 copper review reflect the cited company filings, official orders and study-group releases as of the dates named and can change with the next print or proclamation.