The Iranian nuclear issue should be resolved through diplomatic means, China said on Thursday, just days after Washington had urged new "significant" sanctions against Tehran.

"China''s position remains unchanged and clear: we call for the parties to take measures and steps which would contribute to the proper resolution [of the Iranian nuclear issue] by means of negotiations," Chinese Foreign Ministry spokesman Ma Zhaoxu said.

China, which has traditionally opposed sanctions against Iran, "will continue playing a constructive role" in the resolution of the Iranian nuclear deadlock, the spokesman said.

Earlier this month, China said that discussions of new sanctions against Iran could undermine efforts to resolve the issue using diplomacy.

Ma Zhaoxu did not answer a direct question on whether China would support new sanctions against Iran.

Iran''s nuclear activities sparked a new wave of international criticism earlier this week, after the Islamic Republic announced its plans to enrich uranium to 20%. Western powers fear Iran''s nuclear program is aimed at building weapons, while Tehran insists it needs enriched uranium for civilian power generation.

The Islamic Republic said on Tuesday it had started production of 20%-enriched uranium, which the Iranian authorities say is intended for a research reactor in Tehran.