Copper prices on the London Metal Exchange and Shanghai Futures Exchange were under pressure on Thursday, hovering near a three-week low, amid U.S. President Donald Trump’s plans to start imposing a 50% copper import tariff on August 1.

Trump announced on Wednesday a 50% tariff on copper, saying on social media that the 50% tariff on copper would be effective August 1 and that the decision was made after a national security assessment.

Three-month copper on the LME inched up 0.19% to $9,649 per metric ton by 0111 GMT, and the most-traded copper contract on the SHFE fell 0.75% to 78,320 yuan ($10,913.55). Both were trading close to their lowest levels since late June.

In contrast, the most active COMEX copper futures contract (HGc3) hovered at its record high, and its premium against the LME copper (LMECMXCUc3) jumped to 26% on Wednesday.

“Traders have apparently been very alert and sensitive, only limited cargoes could still reach the U.S. before August 1, so most of them have stopped betting on the premium and higher LME and SHFE prices,” a Shanghai-based metals analyst from a futures company commented.

COMEX inventories (HG-STX-COMEX) are at their seven-year high, and in the coming days, copper supplies may be flown to countries outside U.S., easing regional supply tightness, and the pace will impact SHFE and LME copper prices, the analyst said.

LME aluminium gained 0.27% to $2,603.5 a ton, nickel was up 0.24% to $15,015, tin inched up 0.2% at $33,350, zinc rose 0.2% to $2,748, and lead advanced 0.12% to $2,058.5.

SHFE aluminium gained 0.93% to 20,705 yuan a ton, zinc was up 0.84% at 22,265 yuan, tin rose 0.5% to 264,890 yuan, lead gained 0.26% to 17,245 yuan, and nickel was up 0.12% to 119,600 yuan.