South Korean companies will be very hesitant about investing in the US following a massive immigration raid at a Hyundai plant in Georgia last week, President Lee Jae Myung has said.

More than 300 South Koreans who were arrested in the raid have now been released from detention and are due to return home on Friday after having their release delayed by more than a day.

Their departure was delayed because of an instruction from the White House, Lee added.

President Donald Trump ordered the pause to check whether the workers were willing to remain in the US to continue working and training Americans, according to a South Korean foreign ministry official.

Lee, who was speaking at a news conference to mark the first 100 days of his presidency, said the situation is extremely bewildering, while noting it is common practice for Korean firms to send workers to help set up overseas factories.

If that's no longer allowed, establishing manufacturing facilities in the US will only become more difficult... making companies question whether it's worth doing at all, he added.

Seoul is negotiating with Washington on visa options for South Korean workers whether that means securing [higher] quotas or creating new visa categories, Lee said.

Last week, US officials detained 475 people - more than 300 of them South Korean nationals - who they said were working illegally at the battery facility, one of the largest foreign investment projects in Georgia.

Media in South Korea have described the raid as a shock, raising concerns about its potential impact on investment and business relations with the US.

The White House has defended the operation, claiming it is essential for enforcing immigration laws, while Trump emphasized the need for foreign companies to hire Americans.