Just a day after the G20 free trade summit ended, Japan has restricted exports of some mobile phone components to South Korea.
Relations between the two countries have been less than cordial of late - a ruling by a South Korean court that Japanese companies should pay compensation for using forced labour during the Second World War has not helped. Japan insists that the issue was dealt with when diplomatic relations with South Korea were re-established in the 1960s.
Nevertheless, from Thursday Japan will require companies to apply for individual export licences rather than batch licences for three types of products vital to mobile phone production.
These include "fluorinated polyimides, used to make organic light-emitting diode displays; resistors used in semiconductor production; and hydrogen fluoride, used as an etching gas in chipmaking," according to the Nikkei Asian Review.
Applying and getting approval for individual licences can dramatically slow the supply chain. Japan blamed a breakdown in trust for the move.
Japan will also consider removing South Korea from its "white list" of countries pre-approved to receive equipment with possible security implications.
South Korea slammed the move as unfair and said it would file a World Trade Organisation complaint.
The two leaders – Japanese Prime Minister Shinzo Abe and South Korean President Moon Jae-in – did not have a private meeting at the G20, unlike US prez Donald Trump and Chinese leader Xi Jingping.
Moon Jae-in has previously accused Japan of playing politics with the wartime compensation issue and using it to whip up supporters. ®