China will send a top envoy on arms control to Iran and Russia in an effort to defuse the Iran nuclear standoff with the West, a ministry spokesman said on Thursday, urging restraint on all sides.

Assistant Foreign Minister Cui Tiankai would visit Iran and Russia from April 14 to 18, spokesman Liu Jianchao told a regular news conference.

"We hope the relevant parties can exercise restraint and not take measures that will escalate the situation," Liu said.

Iran declared earlier this week it had enriched its first batch of uranium, in defiance of the United Nations and Western countries which worry its atomic research is aimed at making nuclear weapons.