South Korean President Moon Jae-in has said Japan's actions are politically motivated and have caused an "unprecedented emergency" for his country's export-driven economy.

At the White House, Trump said Moon "tells me that they have a lot of friction going on now with respect to trade, primarily with respect to trade.
Japan has some things that South Korea wants, and he asked me to get involved."

"I like both leaders. I like President Moon, and you know how I feel about Prime Minister (Shinzo) Abe. He's a very special guy also," the president added.

"So if they need me, I'm there."

The row comes with tech companies around the world already under pressure from a weakening global outlook, while the chip sector is particularly threatened by soft demand.

Japanese and South Korean officials held hours of talks on July 12 to discuss their row, without sign of a detente.

That meeting came after the US State Department promised to do "everything we can" to ease tensions between the two US allies.

"We all face shared regional challenges and priorities in the Indo-Pacific and around the world," department spokeswoman Morgan Ortagus said at that time.

All three countries face an increasingly assertive China and the long-running threat of nuclear-armed North Korea.

Senior South Korean official Kim Hyun-chong, on a visit to Washington earlier this month, said the United States wanted high-level three-way talks to resolve the spat, according to the Yonhap news agency.

Ortagus declined to discuss potential meetings, but top US diplomat Mike Pompeo and his two counterparts are all expected to be in Bangkok around the end of the month for meetings of the ASEAN bloc of Southeast Asian nations.

In South Korea, where almost seven in 10 people report negative feelings toward the country's former colonial ruler, the spat has even led beer-lovers to boycott Japanese brews.

E-Mart, the country's largest hypermarket chain, said sales of Asahi, Kirin, Sapporo and Suntory beer fell nearly 25 percent in the first two weeks of July compared with the second half of June.

More broadly, given the volume of trade between the two neighbors, if the restrictions are sustained or expanded it would have "no small impact on our economy", South Korea's central bank chief Lee Ju-yeol told reporters.