South Korea's relations with Japan, including a deal on resolving the issue of wartime sexual slavery, could become "political flashpoints" in the South's upcoming presidential election, thus hampering US efforts to bolster trilateral security cooperation, a congressional report said.

The Congressional Research Service made the point in a report on Japan-US relations, saying that the impeachment of South Korean President Park Geun-hye has "interrupted a steady though delicate improvement" in Japan's relations with Seoul.

Park's impeachment threw into doubt a deal that she reached with Japanese Prime Minister Shinzo Abe in late 2015 to resolve the issue of Japan's sexual enslavement of Korean women for its troops during World War II, a key thorn that had seriously strained their ties for years.

Relations between Seoul and Tokyo soured in recent months as Tokyo railed vehemently against the establishment by South Korean civic activists of a statue of a sexual slavery victim in front of Japan's consulate in the South Korean port city of Busan.
 

The statue's erection came as Japan had demanded Seoul remove another statue in front of Japan's Embassy.

"The deal remains controversial, particularly in light of two statues of comfort women in South Korea, including one located in front of the Japanese Embassy," the CRS said in the report. "The comfort women agreement and overall relations with Japan could become political flashpoints in the upcoming election in South Korea, a development that could hamper US-Japan-South Korea trilateral cooperation."

In the South's presidential election, "more progressive candidates" could target Park's outreach to Japan and reverse some of the initiatives that led to improved relations, including the signing of a bilateral military information sharing agreement, the CRS said.

"A poor relationship between Seoul and Tokyo jeopardizes US interests by complicating trilateral cooperation on North Korea policy and on responding to China's rise," the report said. "Tense relations also complicate Japan's desire to expand its military and diplomatic influence as well as the potential creation of an integrated US-Japan-South Korea ballistic missile defense system."

On security issues, the CRS report said that a lack of confidence in the US security guarantee could prod Japan to reconsider its own status as a non-nuclear weapons state and pursue nuclear weapons, which in turn could lead South Korea to follow suit.

"As a presidential candidate Donald Trump in spring 2016 stated that he was open to Japan developing its own nuclear arsenal to counter the North Korean nuclear threat," the report said, adding that Japan would face a series of consequences, such as sanctions, if it decides to go nuclear.

"If it were to develop its own nuclear weapons, including significant costs; reduced international standing in the campaign to denuclearize North Korea; the possible imposition of economic sanctions that would be triggered by leaving the global non-proliferation regime; and potentially encouraging South Korea to develop nuclear weapons capability," it said.

Meanwhile, as in last year's report, this year's report continued to describe the body of water between South Korea and Japan as the "Sea of Japan," rather than its original name the "East Sea." (Yonhap)