SEOUL, South Korea (AP) -- South Korea's president said Thursday that South Korean companies will likely hesitate to maintain or make direct investments in the United States if the U.S. fails to improve its visa system for Korean workers.

In a news conference marking 100 days in office, Lee called for improvements in the U.S. visa system as he spoke about the Sept. 4 immigration raid in Georgia that resulted in the arrest of more than 300 South Korean workers at a battery factory under construction at Hyundai's sprawling auto plant in Georgia.

Lee said the Korean workers are set to be brought home on Friday aboard a charter plane following negotiations with the U.S.

South Korean and U.S. officials are discussing a possible improvement to the U.S. visa system, Lee said, adding that under the current system South Korean companies "can't help hesitating a lot" about making direct investments in the U.S.

U.S. authorities said some of the detained workers had illegally crossed the U.S. border, while others entered legally but had expired visas or entered on visa waivers that prohibited them from working.

But South Korean experts and officials said Washington has yet to act on Seoul's yearslong demand to ensure a visa system to accommodate skilled Korean workers, though it has been pressing South Korea to expand industrial investments in the U.S.

South Korean companies have been relying on short-term visitor visas or Electronic System for Travel Authorization to send workers who are needed to launch manufacturing sites and handle other setup tasks, a practice that had been largely tolerated for years.

Lee said that whether the U.S. establishes a visa system allowing South Korean companies to send skilled workers to industrial sites will have a "major impact" on future South Korean investments in the U.S.

"It's not like these are long-term workers. When you build a facility or install equipment at a plant, you need technicians, but the United States doesn't have that workforce and yet they won't issue visas to let our people stay and do the work," he said.