Japan reiterated Friday that its new restrictions on high-tech exports to South Korea are not diplomatic countermeasures and do not violate international trade rules.

In their first meeting since the export curbs were put in place last week, officials from Japan's Ministry of Economy, Trade and Industry explained to their South Korean counterparts that the measures are intended to address national security concerns.

South Korea is calling for removal of the restrictions, which it says are retaliation for its handling of a dispute over wartime labor, and has threatened to take the matter to the World Trade Organization.

In their discussions in Tokyo, which went on for much longer than expected at five and a half hours, the Japanese officials said the decision to require individual licenses to export three chemicals -- fluorinated polyimide, hydrogen fluoride and photoresist -- used in the production of semiconductors and display panels comply with WTO rules.

The process to acquire a license, which can take around 90 days, had previously been waived for South Korea, a status it shared with the United States and many European countries.

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Japan had insisted that the meeting was meant to help South Korea understand its reasoning, and did not constitute "negotiations."

The South Korean officials did not push for the restrictions to be lifted in the working-level meeting, according to a Japanese official who briefed reporters.

Japanese Prime Minister Shinzo Abe hinted in a TV appearance last Sunday that the move was connected to U.N. sanctions imposed on North Korea over its nuclear weapon and missile development programs.

South Korea has denied such allegations, and the office of President Moon Jae In said Friday it has proposed asking an international organization to look into the claim.

The restrictions are expected to hurt South Korean exports, of which semiconductors account for around 20 percent. Manufacturers such as Samsung Electronics Co. and SK Hynix Inc. rely on Japanese suppliers for the vast majority of the materials.

The move was announced amid a standstill in a dispute over South Korean court decisions ordering Japanese companies to compensate victims of forced labor during Japan's 1910 to 1945 colonial rule of the Korean Peninsula.

The companies have refused to comply, in line with Japan's stance that the issue of compensation was resolved under a 1965 treaty that established diplomatic relations between the countries. Lawyers for the plaintiffs have threatened to liquidate the companies' seized assets.

Japan has asked South Korea to establish an arbitration panel involving a third country, to resolve the dispute, while South Korea has proposed pooling funds from Japanese and South Korean firms to compensate the victims, but so far neither side has budged.