Iran and the European Union say their talkson Saturday on Tehran's nuclear program were constructive and positive.
An EU spokeswoman says the meeting in Vienna between Iran's top nuclear negotiator, Ali Larijani, and EU foreign policy chief Javier Solana will resume Sunday.
The talks may represent Tehran's last chance to avoid international sanctions for its nuclear program.
In Helsinki on Saturday, China's prime minister urged Iran to consider the international community's concerns about its nuclear program. Wen Jiabao also warned against increasing pressure on Tehran, saying the nuclear standoff should be settled peacefully.
China and Russia have long been reluctant to punish Iran.
The United States is pressing for sanctions on Iran for defying an August 31st UN deadline to suspend uranium enrichment.
The US says it expects the UN Security Council to begin working as early as next week on a resolution to issue sanctions against Iran.
Iran says it will not halt uranium enrichment, which it says is for peaceful uses.