China on Wednesday called for the relevant countries to resume dialogue with North Korea as the U.N. nuclear watchdog warned that the North appears to have restarted its main nuclear bomb fuel plant.

If the warning by the International Atomic Energy Agency is correct, it would be the latest move by North Korea in expanding its nuclear weapons program, despite tightened international sanctions.

When asked about the IAEA warning, China's foreign ministry spokesman Hong Lei replied that China is committed to realizing the denuclearization of the Korean Peninsula and resolving the relevant issues through negotiation and dialogue.

"We hope relevant parties make joint efforts to resume dialogue for the settlement of the Korean nuclear issue," Hong said.

The 5-megawatt reactor in North Korea's Yongbyon nuclear complex has been the source of weapons-grade plutonium for Pyongyang.

In 2013, North Korea threatened to restart all of its nuclear bomb fuel plants.

Earlier this year, U.S. Director of National Intelligence James Clapper said in a worldwide threat assessment that the North had restarted its 5-megawatt reactor and has since run it long enough to harvest plutonium "within a matter of weeks to months."

North Korea has conducted four nuclear tests since 2006. The fourth test in January this year prompted the international community to tighten sanctions against the isolated state. (Yonhap)