A tariff that hasn't happened yet is already moving copper around the world.
Traders are pulling metal out of London warehouses at the fastest pace in over a decade, racing to ship it to the U.S. before Washington decides whether to slap duties on imports.
Copper prices on Comex in New York have pulled ahead of London prices again, with the gap now more than $500 a ton - the widest it's been since last fall.
That spread is what's driving the rush: buy copper in London, sell it in New York at a premium, pocket the difference.
Trafigura, one of the world's biggest commodity traders, did exactly that last week, yanking hundreds of millions of dollars of copper out of London Metal Exchange (LME) warehouses - the largest withdrawal orders the LME has seen since 2013.
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U.S. copper imports had cooled off in recent months as the price gap closed, but industry executives now say imports could jump back to 150,000-200,000 tons a month.
That's a lot of metal pulling out of an already tight market, where supply outside the U.S. is barely meeting demand and Chinese inventories are already shrinking.
If American buyers keep vacuuming up supply, the squeeze lands on London - and getting copper to U.S. ports is getting harder too.
Shipping delays from the Iran war are slowing global routes and jamming up the Panama Canal, the main path for South American copper headed north.
The commerce secretary has until June 30 to deliver an update on the U.S. copper market, and that report could clear the way for refined copper tariffs starting in January 2027 - the Commerce Department called for a 15% duty last year.
Copper is already trading near record highs, hitting $13,746 a ton in London this week - up 43% over the past year.
AI demand has investors more bullish on copper than they've been since December 2020, with Chinese buyers back after the New Year holiday lull adding more fuel.
If duties get confirmed, the back half of 2026 could see a massive rush to beat the deadline, with London stockpiles emptying out fast.
The tariff doesn't need to happen for the trade to keep working - just the threat is enough.
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