Apparently walking a tightrope between its two key regional allies -- South Korea and Japan, the Obama administration continued efforts Monday not to be drawn into a brewing controversy over Tokyo's move to expand its military role.

Japan's conservative Abe government is working to change the interpretation of the pacifist Constitution to allow the nation to exercise the right to "collective self-defense."

It would allow Japan, long restricted to self-defense, to use force against a military attack on the U.S. and other allies.

In the two-plus-two talks between the foreign and defense ministers earlier this month, the U.S. formally supported Tokyo's move.

South Korea, home to 28,500 American troops, has voiced concerned over it, however. Koreans have bitter memories of Japan's militaristic past, especially the 1910-45 colonization of the peninsula and World War II.

South Korean officials said Japan should obtain Seoul's consent to exercise the right to collective self-defense in the event of emergency on the peninsula.

The U.S. State Department said that the issue is associated with Japan's sovereignty.

"It is up to the Japanese people and government to determine Japan's capabilities," the department's press office said in an emailed reply.

It reiterated that the U.S. remains committed to its "deep and long-standing" alliance with Japan.

"We consult regularly with the Japanese government on our respective forces' roles, missions, and capabilities to ensure that our alliance is always ready to carry out its mission to protect Japan and to maintain peace and stability in the region," it added.

In a daily press briefing last week, department spokeswoman Jen Psaki also said how to interpret the Constitution is a matter to be done by Japanese people themselves.

"I know they're looking at their Constitution and a range of other issues. These are decisions, of course, they'll make within Japan. And we discuss them with them," she said. (Yonhap News)