South Korean companies will be very hesitant about investing in the US following a massive immigration raid at a Hyundai plant in the state of 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, with the aim of securing higher quota or creating new visa categories.

I think the US will address this if they see it as a practical necessity, Lee commented.

Last week, US officials detained 475 people - including over 300 South Koreans - who were allegedly 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, warning it could have a chilling effect on business activities within the US. The Yonhap News Agency published an editorial urging cooperation between the two countries to repair any damage to their alliance.

The timing of the raid, coinciding with sensitive trade discussions between the two governments, has raised alarms in Seoul.

The White House has defended the operation at the Hyundai plant, stating that it does not expect the raid to deter foreign investment.