Russia and the US have pledged to work together to ensure Iran's nuclear program is for peaceful purposes.

After talks in Moscow with her counterpart Sergei Lavrov, US Secretary of State Hillary Clinton said Iran remained a "matter of serious concern", the BBC reported.

She said the US was not seeking further sanctions at this stage. Lavrov said Russia was "very reserved" about it.

Iran, which has recently revealed a second uranium plant, insists its nuclear programme is peaceful.

Clinton, in Moscow at the end of a European tour, praised Russia for its "extremely cooperative" work with world powers over the Iranian nuclear crisis.

"We believe Iran is entitled to peaceful energy but is not entitled to nuclear arms," she told reporters. "Russia agrees with us on that."

The secretary of state added that if current talks between world powers and Iran failed, further sanctions might be inevitable - but she re-iterated that negotiation was still the preferred route at this stage.

Lavrov said neither country had asked the other for anything in dealing with Iran, but "our positions coincide".

The US secretary of state is due to meet President Dmitry Medvedev at his private residence outside Moscow later.