BEIJING - China on Wednesday called on all concerned parties to enhance diplomatic efforts for a comprehensive, long-term and proper resolution regarding Iran's expanding nuclear program.

Foreign Ministry spokesman Liu Weimin made the comment in response to a question at a regular press briefing in Beijing.

"The priority for resolving Iran's nuclear issue is to step up diplomatic efforts and resume dialogues and negotiation between Iran and the G5+1 at an early date," Liu said.

Iran confirmed that it has begun uranium enrichment at an underground bunker attached to its Fordo nuclear facility, Iranian diplomats said on Monday at the International Atomic Energy Agency (IAEA)'s headquarters.

The facility was built near the Shiite holy city of Qom and is being used to produce 20-percent enriched uranium, which can be used to create nuclear weapons.

"We have noticed relevant reports," Liu said, adding that China recognizes that Iran's nuclear facilities are under the guarantee and supervision of the IAEA.

China hopes that Iran will further strengthen its cooperation with the IAEA and clarify pending problems with its nuclear program as soon as possible, Liu said.