US President Donald Trump said last week that he would impose a 25 percent tariff on imported steel and a 10 percent levy on imported aluminium to protect US producers, risking retaliation from major trade partners like China, Europe and neighbouring Canada.
"We want Trump to abandon the plan," Yoshihisa Tabata, executive director of the Japan Aluminium Association told Reuters on Monday by phone.
"The US is the second-biggest exporting market after China for Japanese aluminium producers and the high duties will directly impact on their business," he said.
Japan, which produced 2.07 million tonnes of rolled and extruded aluminium in 2017, exported about 27,000 tonnes to the US out of total exports of about 243,000 tonnes.
"If the new tariffs were slapped, low-end commodities among Japanese aluminium products will be quickly replaced by US-made products although high-end aluminium may take a while to be switched," he said.
The tariffs are expected to cause higher volatility in metal prices and in the premiums that are paid by buyers on top of exchange prices to cover insurance and the cost of delivery, he said.
"Producers and buyers will have to face unexpected changes in aluminium prices and premiums going forward," he said.
The Aluminium Association had previously expressed concerns about potential US tariffs, with Mitsuru Okada, the head of the association, saying last July that any US trade action to curb imports may result in surplus supply elsewhere and prompt a chain-reaction of retaliation by other nations.
Tabata echoed those concerns again on Monday.
"If the US tariffs prompt retaliation from other countries and triggers a trade war, aluminium output will eventually shrink as producers will be making products only to meet local demand," Tabata said.
"That would be a nightmare."