Seven U.S. trade partners have formally opposed a federal investigation examining whether copper imports threaten national security.
Each government argued in letters that are now public that its exports strengthen U.S. supply chains and do not impair defense, energy, or infrastructure readiness.
The investigation was initiated March 10 under Section 232 of the Trade Expansion Act of 1962.
“Copper is a critical material essential to the national security, economic strength, and industrial resilience of the United States,” the executive order states. “Copper, scrap copper, and copper’s derivative products play a vital role in defense applications, infrastructure, and emerging technologies, including clean energy, electric vehicles, and advanced electronics. The United States faces significant vulnerabilities in the copper supply chain, with increasing reliance on foreign sources for mined, smelted, and refined copper.”
Chile, the United States’ largest supplier of refined copper, said in a letter that its exports are essential for American industries.
“Copper imports from Chile contribute to the United States’ supply chain security and do not represent any risk to its national security interests,” Chilean Ambassador Juan Gabriel Valdés wrote in the letter.
Canada emphasized its role as a close ally and top destination for U.S. copper exports, noting that bilateral copper trade benefits both economies and supports defense-related manufacturing.
The Canadian government, in its letter, said that “imports of Canadian copper do not in any way threaten to impair U.S. national security.”
“In fact, the opposite is true–imports of copper from Canada support U.S. national security and complement efforts from U.S. domestic industries to reinforce supply chains,” they wrote. “Copper producers in both Canada and the United States are vulnerable to market manipulation by non-allied producers across the supply chain, especially in the copper refining segment. Canada therefore shares the United States’ interest in reducing dependence on imports from non-market-based producers in non-allied countries.”
Peru said its exports help meet U.S. demand for copper used in clean energy, transportation, and electronics, and cited a 2024 memorandum of understanding with the United States on critical minerals cooperation.
“First, the Government of Peru can confidently affirm that Peruvian copper exports do not pose a threat to the national security of the United States,” the country’s Ministry of Foreign Trade and Tourism stated. “Peru is a reliable trading partner that contributes to the security of the United States copper supply chain and also strengthens the competitiveness of various strategic industries such as electronics, renewable energy, and automotive, by supplying products such as copper cathodes, copper bars and profiles, refined copper wire, copper plates, and strips, that is, essential inputs for key U.S. industries.”
Indonesia warned that any new measures could raise costs for U.S. manufacturers and reduce American copper exports to Indonesian buyers. The government said U.S. companies have invested heavily in Indonesia’s mineral sector and would face uncertainty under new trade restrictions.
South Korea pointed to its investments in U.S.-based battery and electronics production. Korean officials said copper from South Korea is mostly used in construction and civilian infrastructure, not defense, and cautioned that new tariffs could hurt industrial growth.
China called the investigation unnecessary and said its copper exports to the United States are minimal. It stated that invoking national security in trade disputes risks undermining global supply chain stability.
Meanwhile, the European Union echoed those concerns, stating that its exports are crucial to U.S. energy and manufacturing sectors and should not be targeted.
Section 232 investigations must be completed within 270 days, according to Trump’s executive order, which would place the current review on track to conclude in November.
The agency has not released any preliminary findings and did not respond to a request for comment on the letters or a status update on the investigation before publication.
