US President Donald Trump said on Sunday that foreign companies need to hire and train American workers and respect immigration laws, following a raid at a Hyundai Motor manufacturing facility in the US state of Georgia last week.

South Korea is moving to pick up some 300 South Koreans who were detained after the raid.

US federal agents arrested about 475 workers at Hyundai's car battery plant in Ellabell, Georgia, on Thursday.

"Following the Immigration Enforcement Operation on the Hyundai Battery Plant in Georgia, I am hereby calling on all Foreign Companies investing in the United States to please respect our Nation's Immigration Laws," Trump wrote on Truth Social.

"Your Investments are welcome, and we encourage you to LEGALLY bring your very smart people, with great technical talent, to build World Class products, and we will make it quickly and legally possible for you to do so. What we ask in return is that you hire and train American Workers."

Trump made the post shortly after telling reporters he would look at what happened but that the incident had not harmed his relationship with South Korea.

He also floated the idea that he would look at the possibility of some foreign manufacturing experts being allowed into the country to help train American workers.

RTHK's Washington correspondent, Simon Marks, said the raid by the US Immigration and Customs Enforcement, or ICE, had been planned for months.

"This was not a random raid. We, of course, have seen so many random ICE raids targeting migrants all over the United States since President Trump became president. But this followed what the Department of Homeland Security describes as months of investigation and surveillance," he told Hong Kong Today.

Marks added the arrests add a "significant wrinkle" to trade conversations between the US and South Korea going forward.

"The South Korean Foreign Minister, Cho Hyun, says that he'll be heading to Washington, DC on Monday ... and understand exactly why those 300-plus South Koreans were targeted, and what the two countries can do in the future to avoid any repeat of this," he said.

The South Korean government has expressed regret about the arrests and the release of the footage showing the operation involving armoured vehicles detaining the workers who were shackled and taken in. (Reuters)