Japan has been working with the United States to join a U.N.-led nuclear inspection team in North Korea, assuming Pyongyang agrees to accept the inspectors, according to sources close to Japan-U.S. relations.

The government recognizes the need to be involved in the International Atomic Energy Agency's inspection of the Yongbyong nuclear complex because Japan faces a "nuclear threat," according to the sources.

The move signals Tokyo's efforts in playing an active role in North Korea's denuclearization process, instead of just trusting the United States and other global nuclear powers, they said.

The government is considering sending government and private-sector nuclear experts.

In June, Japan and the United States stressed the need for an IAEA inspection at the third round of the six-nation talks held in Beijing, also attended by Russia, China, North Korea and South Korea.

North Korea agreed to discuss inspections in the multilateral talks but opposed a survey by the U.N. nuclear watchdog.

The sources also said Japan and the United States agreed last week to form an inspection framework involving Japanese experts when they held a working-level meeting in Washington.