There had been some concern that the South Korean outfits might have some problems due to the US’s trade war with the US.

South Korean senior presidential secretary for economic affairs Choi Sang-mok said the US had already told the companies of their decision and it is up and running.

"Uncertainties about South Korean semiconductor firms' operations and investments in China have been greatly eased; they can seek long-term global management strategies calmly," he said.

The U.S. Department of Commerce is updating its "validated end user" list, denoting which entities can receive exports of which technology, to allow Samsung and SK Hynix to keep supplying specific U.S. chipmaking tools to their China factories, the presidential office said.

Once included in the list, there is no need to obtain permission for separate export cases. Samsung and SK Hynix, the world's largest and second-largest memory chipmakers, had invested billions of dollars in their chip production facilities in China and welcomed the move.