Japan's military won't operate on the Korean Peninsula without Seoul's consent, a senior U.S. diplomat handling relations with Seoul and Tokyo said Tuesday.

Japan's decision to exercise so-called "collective self-defense" has spurred concern in South Korea that the former colonial master might abuse the right and enter the Korean Peninsula without Seoul's consent in the event of a contingency with North Korea.

Japanese Defense Minister Gen Nakatani, after talks with his South Korean counterpart in Seoul earlier Tuesday, maintained that the country won't be involved in any military operation in South Korea without Seoul's consent.

But Nakatani remained noncommittal about whether Japan should seek Seoul's consent before entering North Korea, only saying that the U.S., South Korea and Japan should cooperate on the matter.

Amb. Sung Kim, U.S. deputy assistant secretary of state in charge of relations with South Korea and Japan, said that it's clear that Japan would not operate on the peninsula without Seoul's consent.

"If you look at the revised guidelines between US and Japan, it very clearly states the importance of respecting the sovereignty of a third country," Kim told reporters after a Senate Foreign Relations Committee hearing. "It's obvious that Japan would not operate on the peninsula without South Korea's consent."

The collective self-defense right empowers Japan to fight alongside its allies even when not under attack itself, a move that had been considered impossible under Japan's pacifist constitution.

But the administration of nationalist Prime Minister Shinzo Abe made it possible by reinterpreting the constitution.

The U.S. has welcomed the initiative, apparently seeing it as helpful in countering China's rise. The initiative is the centerpiece of the new Guidelines for U.S.-Japan Defense Cooperation, adopted in April.

Critics have denounced collective self-defense as a precursor to Japan ultimately amending the country's constitution. South Korea views the move warily as it calls to mind Japan's past militarism amid concerns that the power could be misused. (Yonhap)