Diplomacy remains the best way to address a growing crisis over Iran's nuclear ambitions, Chinese Foreign Minister Li Zhaoxing said in Oslo on Monday, emphasizing however that "time is already pressing" for Tehran.

"China believes that peace is more important and more valuable than anything in the world," Li told reporters following a meeting with his Norwegian counterpart Jonas Gahr Stoere.

"In addressing the Iranian nuclear issue, we have to bear in mind that a diplomatic solution serves the common interest of all parties," he added.

Iran on Monday officially notified the International Atomic Energy Agency that it would resume full-scale uranium enrichment, ending a two-year-old freeze on the work in response to an IAEA vote over the weekend to report it to the UN Security Council.

In Oslo, Li called on Tehran to return to the negotiating table.

"Time is already pressing," he said, adding that Beijing was "still encouraging and working (with) Iranian colleagues of ours to cherish the negotiations … so that conditions can be … created for resolving the issue within the framework of the IAEA."

US diplomats meanwhile refused on Monday to rule out sanctions against Iran if it continues its sensitive atomic activities.

The UN nuclear watchdog is scheduled to meet again on March 6 to determine whether Iran has lived up to the resolutions reached in Saturday's meeting.