South Korean auto giant Hyundai on Monday announced a multi-billion-dollar investment in the United States, including a new US$5.8 billion steel plant.

The plant, which will be based in the US state of Louisiana, "will create 1,300 American jobs," Hyundai executive chairman Euisun Chung told reporters at a White House event alongside President Donald Trump.

With an annual capacity of 2.7 million tonnes, it is part of Hyundai's US$21 billion investment in the US.

Hyundai's announcement makes it the latest firm to announce plans to invest billions of dollars into the United States since Trump's return to power in January.

The US president has repeatedly threatened to impose painful tariffs on companies that do not relocate manufacturing jobs to the United States from overseas.

In response, domestic and foreign firms, including Apple and Oracle, have announced plans to invest hundreds of billions of dollars into US projects over the next four years.

"Cars are coming to this country at levels never seen before," Trump told reporters on Monday.

The investment was "a clear demonstration that tariffs very strongly work," he said.

"Hyundai will be producing steel in America and making its cars in America, and as a result, they'll not have to pay any tariffs," he added. (AFP, with additional reporting by Reuters)