Tension appears to be building between the U.S. and Japan as Tokyo’s moves to enhance ties with Pyongyang and Moscow have apparently unnerved Washington, which has imposed tough sanctions against the two.

Tokyo’s controversial reexamination of its 1993 apology for its wartime sexual enslavement of Korean women is also a source of concern for Washington as it would escalate historical feuds between Japan and South Korea, and hamper the three-way security collaboration.

Although the U.S. and Japan shared the common strategic goal of curbing China’s assertiveness, Tokyo’s recent diplomatic course is burdensome for Washington, observers said.

The Shinzo Abe administration has been reviewing the “background” of the so-called Kono Statement in recent months. It is expected to submit a report to the Diet before its session ends this Sunday.

Along with the 1995 Murayama Statement carrying an apology for Japan’s colonial occupation of Asian states including Korea, the Kono Statement has been regarded as a milestone that brought bilateral relations to a new level.

Any attempt to damage the spirit of the Kono Statement is expected to seriously damage relations between Seoul and Tokyo, which will make it difficult for Washington to strengthen the triangular defense cooperation for regional stability, analysts say.

Tokyo’s moves to enhance ties with Pyongyang have also been triggering concerns. Last month, Japan and the North announced their agreement to investigate the abduction of Japanese nationals and lift Tokyo’s independent sanctions against Pyongyang with the beginning of the probe.

The agreement has spawned worries that the international efforts to persuade Pyongyang to give up its nuclear program could falter as Japan, with the lifting of its sanctions on the North, would weaken international pressure on the communist state.

Tokyo and Russia’s increasing diplomatic contacts also seem to have vexed Washington. Earlier this month, Russian parliament speaker Sergei Naryshkin, a close aide to President Vladimir Putin, visited Japan for cultural exchanges. Naryshkin is one of the Russian officials who the U.S. listed for asset freezes in connection with the Ukraine crisis.

During his stay in Japan, Naryshkin met key Japanese politicians, exhibiting their stable political ties. Putin is also scheduled to visit Japan in September amid the continuing East-West standoff over Russia’s annexation of the Crimean peninsula.

Another source of friction between the U.S. and Japan is their differences over details of the Trans Pacific Partnership, a proposed free trade pact linking Pacific-rim states. The two sides have yet to resolve their differences over major items such as rice and beef.

During President Barack Obama’s latest visit to Japan in April, Obama was reported to expect Japan to make some concessions over the TPP, but he returned home empty-handed, despite his show of strong U.S. security commitment to the defense of disputed islands in the East China Sea, called Senkaku in Japan and Diaoyu in China.

Amid brewing tension, Obama reportedly rejected Abe’s request for a summit on the sidelines of the G7 summit in Brussels, Belgium, earlier this month. They ended up talking for only five minutes, reports said.

Analysts, however, concur that they would continue to strengthen the bilateral alliance to better deal with North Korea and China. Japan’s push for collective self-defense, marine forces and a stronger military establishment has been welcomed by the U.S.

By Song Sang-ho (sshluck@heraldcorp.com)