Russia has traditionally resisted threats of tough action against Iran over fears it is developing a nuclear bomb, but Iran's announcement that it has started work to produce 20 percent enriched uranium heightened concerns in Moscow.

"Iran claims it is not trying to acquire nuclear weapons," Nikolai Patrushev, secretary of Russia's security council, was quoted as saying by news agencies.

"But actions such as starting to enrich low-enriched uranium up to 20 percent raise doubts in other countries and these doubts are fairly well-grounded," Patrushev added.

While the United States and France have already pressed calls for "strong" new sanctions against Iran, China is now the main power holding out.

China again called for talks on a nuclear fuel deal with Iran.

"We hope the relevant parties will exchange views on the draft deal on the Tehran research reactor and reach common ground at an early date which will help solve the issue," foreign ministry spokesman Ma Zhaoxu said.

"I hope relevant parties will step up efforts to push forward dialogue on this question."

Turkish Foreign Minister Ahmet Davutoglu will visit Iran next week to push for a diplomatic solution to the stand-off, a Turkish diplomat said. The international group has proposed enriching uranium for Iran, but that deal now appears close to collapse.

But the Turkish minister said in Ankara: "The proposal is still valid ... We believe there is still an important chance" for peace. He added that he plans to meet President Mahmoud Ahmadinejad and Foreign Minister Manouchehr Mottaki in Tehran.

The United States has called the latest Iranian moves "provocative" and is pressing ahead with moves at the UN Security Council for a fourth sanctions resolution against Iran.

US Defense Secretary Robert Gates "thinks this is a matter of weeks, not months," Pentagon spokesman Geoff Morrell told reporters in Paris where Gates met French President Nicolas Sarkozy.

"He thinks that we need it and that we can do it in that time," Morrell added. "In all his meetings he discussed this sense of urgency."

Sarkozy and Gates on Monday agreed to push for "strong" new anti-nuclear sanctions against Iran, which insists its atomic drive is to produce energy.

Gates told the US news channel Fox on Monday night that a new resolution would provide "a legal platform for the EU and individual countries to perhaps take even more far-reaching steps" against Iran.

The UN Security Council has already passed three sanctions resolutions against Iran.

France holds the presidency of the council this month. But its Foreign Minister Bernard Kouchner said Monday that China's opposition could prevent any resolution being passed during February.

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