Iran's chief nuclear negotiator Saeed Jalili arrived in China on Thursday to discuss the Islamic republic's atomic programme with Beijing, which has opposed new sanctions against Tehran.
A spokesman for the Iranian embassy in Beijing confirmed Jalili arrived in the morning but declined to provide further details on his visit.
Jalili was to meet high-ranking officials in Beijing and hold "bilateral talks and discuss the nuclear issue" Iran's official IRNA news agency reported earlier.
His visit comes amid mounting pressure against Iran to abandon its suspect nuclear programme, with US President Barack Obama saying Tuesday he wants sanctions agreed on within weeks.
China has resisted calls for new sanctions and called for stepped up negotiations.
But the US ambassador to the United Nations, Susan Rice, said Wednesday that China now appeared ready for "serious" talks at the UN on the issue.
"China has agreed to sit down and begin serious negotiations here in New York," Rice told CNN.
China has a close diplomatic and trade relationship with Iran, dominated by its imports of Iranian energy resources, and its position remains key to the future of the long-running stand-off.
The UN Security Council has already slapped three rounds of sanctions on Iran over its refusal to halt uranium enrichment, which the West and Israel view as a cover to build nuclear weapons.
Oil-rich Iran insists its nuclear program is needed for electricity generation.
Jalili plans to hold a press briefing in Beijing on Friday.