Japan's trade ministry says it has asked the South Korean government to explain why it plans to remove Japan from its top-tier list of countries subject to preferential export procedures.
Seoul announced the measure last month and invited public opinions on it from August 14 through Tuesday.
The Japanese ministry said on Tuesday that it had submitted a public comment and questions to the South Korean government.
The ministry says if the South Korean government goes ahead with the plan without giving clear answers to the questions, Japan will have to consider it to be a retaliatory measure that is groundless and arbitrary.
The ministry also says it wants Seoul to give detailed reasons for the move and cite the laws on which the measure is based.
If Japan is dropped from Seoul's list of trusted trading partners, companies will have to submit more documents to import products from South Korea to Japan, and the screening process is expected to take longer.