Copper prices increased in New York and London on Monday, marking the start of a crucial month that is expected to provide more clarity on the Trump administration's plans to impose tariffs on U.S. metal imports. According to Jin10, U.S. Commerce Secretary must submit the latest recommendations on refined copper tariffs to President Donald Trump by June 30. Ahead of this decision, the premium of U.S. prices over other regions has widened again, prompting metals to flow back to U.S. ports. This adds to other supportive factors keeping copper prices high, which have already risen 5% in May. Efforts for a ceasefire between the U.S. and Iran have also boosted metal prices, while enthusiasm for AI-related assets has spread to the copper market. Goldman Sachs has raised its outlook for copper prices on the London Metal Exchange, increasing its year-end forecast by over 10%, citing U.S. stockpiling and weaker-than-expected mine supply as reasons for a tight market. The bank predicts copper prices will reach $13,735 per ton by the end of 2026, up from a previous forecast of $12,465 per ton.