South Korea’s major semiconductor manufacturers are attempting to reassure their global corporate clients amid concerns Japan’s restrictions of high-tech material exports will slow their supply.

According to multiple industry sources on Thursday, Samsung Electronics sent a letter on Tuesday to clients saying it will do all it can to avoid supply disruptions and that would be fully transparent if any issues arise.

SK Hynix is also known to have sent a similar letter to its clients. 

The two companies combine to make up over 70 percent of the global DRAM(dynamic random-access memory) market and 50 percent of the global NAND flash memory market. 

On Thursday, Tokyo expanded export controls to South Korea of key materials used in the production of these and other high-tech parts manufacturing, raising concerns of a possible interruption to global supply chains.