With world powers locked in talks in New York over a draft resolution that would impose sanctions over Iran's failure to halt uranium enrichment, Tehran has defiantly expanded work on the process at a key nuclear plant.

But Iran's foreign ministry spokesman Mohammad Ali Hosseini did not appear concerned that sanctions were imminent, saying there was a split between the stances of China and Russia on one hand and Europe and the US on the other.

"Splits between the parties are very visible, that is to say between the United States and the Europeans on one side and Russia and China on the other," foreign ministry spokesman told reporters.

"These two countries have completely different positions to the Europeans. Russia does not want sanctions and does not want to close the path of negotiations, and the Chinese have a similar position," he added.

The United Nations Security Council's five veto-wielding members -- Britain, China, France, Russia and the US -- as well as Germany have been discussing a draft resolution on sanctions put forward by European countries.

But in a sign of the difficulty in reaching an agreement, Russian Foreign Minister Sergei Lavrov rejected the proposed sanctions, arguing that they did not advance objectives agreed on by the six world powers.

The Chinese stance has yet to become clear, although Beijing -- like Moscow -- is an economic ally of Iran and traditionally reluctant to use sanctions as diplomatic leverage.

Hosseini meanwhile played down Iran's move to start enriching uranium from a second cascade of 164 centrifuges at its nuclear plant at Natanz in the centre of the country, a decision greeted with suspicion by the West.

"The second cascade is part of the research activities of the country which are in line with the nuclear Non-Proliferation Treaty," he said.

"There is nothing new. It is the continuation of legal activities under the control of the International Atomic Energy Agency (IAEA), and there is no deviation," Hosseini added.

Iran vehemently rejects US allegations that its nuclear programme is aimed at making nuclear weapons, saying the drive is solely aimed at providing energy for civilians.

Enriched uranium lies at the centre of the dispute over Iran's nuclear programme, as it can be used both to make nuclear fuel and, in highly refined form, the core of a nuclear bomb.

Iran would need thousands more such centrifuges to enrich uranium on an industrial scale and its current uranium enrichment work is on a research level only.

Officials have said that uranium was successfully enriched from the second cascade of centrifuges to a level of 3-5 percent and has now been put into storage.

To make a nuclear bomb, the uranium needs to be enriched to around 90 percent, far above the level needed for nuclear fuel.

The text drafted by Britain, France and Germany in consultations with Washington calls on UN member states to slap ballistic missile-related and nuclear sanctions on Iran.

It provides for a freeze of assets related to Iran's nuclear and missile programmes and travel bans on scientists involved.

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