Copper Gravity: US Inventory, Tariffs and LME Prices

22/10/2026

Copper Gravity: F = mg

When government influence changes the economics of physical availability

The US has accumulated a substantial strategic advantage in copper without having to purchase the metal itself. But keeping that inventory on American soil could prove considerably more expensive for the rest of the world - and ultimately for the United States.

The tariff dilemma

There is a reasonably well-established formula for what we might expect if the US administration removes the threat of tariffs on copper cathode.

The COMEX premium would likely contract substantially, the incentive to accumulate additional inventory in the United States would diminish, and some of that metal might eventually find its way back into international markets.

But the Trump administration faces an interesting dilemma.

While keen to relieve inflationary pressure, it also has a strategic interest in the substantial copper inventories accumulated in North America.

With US holdings estimated at approximately 1.6 million tonnes, and some estimates approaching 2 million tonnes, much of this inventory has been assembled and financed by private market participants without requiring the government to purchase it directly.

Which brings us to a slightly different formula for copper gravity. For those who recall their school science lessons:

F = mg

F  Force of retention     ·     m  Mass of inventory     ·     g  Government influence

The tariff threat has already demonstrated its ability to influence the geographical distribution of copper. The more interesting question is how much government influence is required simply to keep it there.

Attracting copper is one thing. Releasing it is another.

There is an important distinction between attracting inventory and determining whether it subsequently moves.

The arbitrage that encouraged copper into the United States can disappear without creating an equivalent incentive for that metal to move back out. Exporting copper incurs costs, while holding it preserves the potential advantage of domestic availability ahead of any future tariff barrier.

Whether that advantage would be surrendered upon export is less certain, given the potential for favourable customs treatment of qualifying returned goods and the unresolved application of any future cathode tariff.

Nevertheless, even a modest probability of future tariffs may discourage inventory holders from releasing metal, particularly where the alternative offers little immediate economic advantage.

The administration may not need to implement tariffs to preserve the strategic advantage its policies have created. Continued uncertainty may be sufficient.

But there is a circularity here, and ultimately a reckoning over priorities.

If the administration succeeds in moderating tariff expectations and reducing the COMEX premium without triggering significant outflows, it may achieve its strategic objective without controlling the consequences for international prices.

When visible inventory becomes unavailable inventory

The cessation of exceptional US imports could initially improve international availability at the margin. However, the substantial inventories already accumulated in North America would remain less accessible to the rest of the world unless relative prices moved sufficiently to justify their return.

Should the market subsequently become uncomfortable with the volume of inventory actually available outside the US, the first significant adjustment may be seen in the LME or SHFE forward curves.

A tightening of nearby spreads, potentially into pronounced backwardation, would reflect increasing competition for immediately available metal, even while headline global inventories remained substantial.

HOW THE PRESSURE COULD DEVELOP

01 US inventory remains in place COMEX premium declines without a matching release of metal

02 Available copper outside the US tightens Regional availability increasingly determines pricing

03 LME / SHFE nearby spreads strengthen Forward curves may move toward backwardation

04 Reverse arbitrage becomes attractive International prices eventually reward US metal exports

There may also be a secondary consequence for COMEX.

Any corresponding tightening of its forward curve would reduce the contango available to inventory holders, potentially diminishing the attractiveness of maintaining those positions. This would introduce another consideration into the decision to retain or release metal, even before regional price differentials became sufficient to justify physical movement back into international markets.

Ultimately, any requirement to mobilise American inventories would demand a sufficiently favourable reverse arbitrage, potentially involving a significant appreciation in LME prices relative to COMEX, whether through higher LME prices, lower COMEX prices or some combination of the two.

The market may therefore find itself pricing an increasingly uncomfortable shortage of accessible copper, even while substantial inventories remain visible elsewhere.

The inflationary price of strategic security

If that produces higher LME prices, stronger physical premiums or tighter forward curves outside the United States, the consequences will not necessarily remain outside its borders.

Higher copper prices could compound inflationary pressures across infrastructure, manufacturing and electrification, potentially complicating the Federal Reserve's efforts to ease monetary policy.

There is therefore a literal price to be paid for strategic inventory.

 There is also a question of duration. Additional production, secondary supply and adjustments in consumption may eventually allow international markets to accommodate the effective withdrawal of US inventories, but current refined copper forecasts suggest this could take years rather than months.

Meanwhile, privately owned inventories will ultimately have a price at which their owners are prepared to release them. As international prices rise relative to US prices, the incentive to overcome the costs and perceived risks of exporting that metal becomes increasingly compelling.

The administration therefore faces a choice between objectives that may not be entirely compatible: maintaining a strategic stockpile and encouraging lower commodity prices.

The US may be able to keep the inventory without maintaining the COMEX premium, but it cannot assume the rest of the world will continue pricing copper as though that inventory were freely available.

The gravitational limit

Copper Gravity is therefore not simply about the force required to hold the metal in place. It is about the price the rest of the world must pay for its absence, and the point at which that price becomes sufficient to overcome the force holding it there.

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