...

The dispute stems from Japan’s frustration over what it sees as South Korea’s failure to act in response to a ruling by one of its courts last October ordering Japan’s Nippon Steel Corp (5401.T) to compensate former forced laborers.

Japan says the issue of forced labor was fully settled in 1965 when the neighbors restored diplomatic relations.

The countries share a bitter history dating to Japan’s colonization of the Korean peninsula from 1910 to 1945, which saw forced use of labor by Japanese companies and the use of “comfort women”, a Japanese euphemism for girls and women, many of them Korean, forced to work in its wartime brothels.

The United States has been dismayed by the dispute and its new senior diplomat for East Asia, David Stilwell, will visit both countries on his first trip to the region this month.

A spokeswoman for the U.S. State Department said it was “critical to ensure strong and close relationships between and among our three countries in the face of shared regional challenges” including that posed by North Korea.

She said all U.N. member states were required to implement sanctions resolutions and added: “The United States and South Korea coordinate closely on our efforts related to (North Korea), and we mutually work to ensure that U.N. sanctions are fully implemented.”

The State Department said Stilwell, the assistant secretary of state for East Asia and the Pacific, would visit Japan from Thursday to Sunday and South Korea on July 17.

The export curbs come weeks ahead of a July 21 upper house election that Abe’s Liberal Democrats and their junior partner are expected to win with a solid majority.

“Unfortunately, the election is coming,” said one person familiar with the Japanese government’s thinking. “The LDP will do anything to solidify their support base.”

Lee Young-chae, a professor at Keisen University in Tokyo, also said politics seemed to be a factor.

“One issue that could lead to an election win seems to be rallying Abe’s conservatives and consolidating swing voters by showing an anti-South Korea, a tough stance toward South Korea,” Lee said. “And it seems to be working.”