Two South Korean steelmakers said they were considering new investment options in the United States, while Europe's steel mills warned of a flood of surplus metal as increased tariffs on U.S. steel and aluminium imports came into force on Wednesday.

President Donald Trump officially increased tariffs on all steel and aluminum imports to 25% on Wednesday, promising that the taxes would help create U.S. factory jobs at a time when his seesawing tariff threats are jolting the stock market and raising fears of an economic slowdown.

The European Union announced countermeasures targeting the U.S. after President Donald Trump's 25% tariffs on steel and aluminum imports came into effect.