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Iran's foreign minister said Thursday that four unspecified issues must be resolved before his country agrees to a proposed Russian solution to the standoff over his nation's nuclear ambitions.

China, meanwhile, was sending an envoy to Tehran in a last-ditch effort to broker a deal before a meeting of the U.N. nuclear watchdog next month that could start a process leading to possible U.N. Security Council sanctions.

"We are ready to compromise," Iran's Foreign Minister Manouchehr Mottaki told reporters during a brief visit to Indonesia as part of an Asian tour that will take him to Thailand on Friday.

Moscow has proposed moving Iran's enrichment of uranium to Russian soil to assuage international fears that the theocracy could produce atomic weapons. Enrichment is a process that can produce fuel for a nuclear reactor or material for a warhead.

Mottaki said that four issues remain unresolved, among them which countries and companies would be involved. But "if you ask me, the main element is timing and place or places," he said, without elaborating.

"We believe that we should move from here to compromise, not go back."

The United States and other Western governments suspect that Iran's nuclear program is a cover for producing weapons, but Tehran insists it only wants to develop energy.

Russian talks with Iranian officials on the compromise proposal this week ended with no signs of progress. The head of Russia's atomic energy agency was set to travel to Iran on Thursday for further talks on Moscow's proposal.

Russian President Vladimir Putin said Wednesday that negotiations were proving difficult.

He said that the Kremlin's offer to enrich uranium in Russia should be "perfectly acceptable" to Iran.

"We are not losing optimism," Putin said. "We are waiting for a final response from the Iranian negotiators and we hope for a positive result."

The International Atomic Energy Agency meets March 6 to discuss the standoff and could start a process leading to a review by the Security Council, which has the authority to impose sanctions on Iran.

China, a commercial partner of Iran that wants to avoid sanctions, announced Thursday that it was sending Vice Foreign Minister Li Guozheng to Tehran on Friday for a three-day visit to discuss the crisis.

"They will exchange views on the nuclear issue," Foreign Ministry spokesman Liu Jianchao said. "We will discuss how to resolve this issue ... properly through dialogue and consultation.

"We hope the relevant parties could exercise patience and restraint, and now there's still room for a solution of this issue within the IAEA."