The US secretary of state, in Moscow at the end of a five-day European tour, told a joint news conference with Mr Lavrov that Russia had "been extremely co-operative in the work that we have done together" on Iran.

Iran says its nuclear programme is for peaceful energy purposes, but the US and other Western nations believe it is seeking nuclear weapons.

Tehran revealed last month that it had a second uranium plant, further raising questions about the nature of its nuclear ambitions.

'No requests'

Ahead of Mrs Clinton's visit, a US official had suggested she would ask Russian leaders about "specific forms of pressure" that Moscow would be prepared to back if talks failed.

But Mrs Clinton said no requests had been made.

"We did not ask for anything today. We reviewed the situation and where it stood, which I think was the appropriate timing for what this process entails," she said.

The US was not seeking further sanctions pending talks between big powers and Iran, she added, but could do so "in the absence of significant progress and assurance that Iran is not pursuing nuclear weapons".

Mr Lavrov, for his part, said "all efforts" should be made to maintain dialogue with Iran.

"We are convinced that threats, sanctions, and threats of pressure in the present situation are counter-productive," he said.

The BBC's Rupert Wingfield-Hayes in Moscow says Mrs Clinton was looking for a solid commitment from Mr Lavrov, but did not get one.

Both Mr Lavrov and Mrs Clinton also said there had been considerable progress in talks on a new treaty to reduce the two countries' nuclear arsenals.

Mrs Clinton later met President Dmitry Medvedev at his Barvikha residence, but she will not meet Russia's powerful Prime Minister, Vladimir Putin.

He is in China for talks focusing on trade, but also expected to raise the nuclear programmes of Iran and North Korea.

No quid pro quo

President Barack Obama, who met Mr Medvedev in July, has pledged to reset relations with Russia.

A month ago, following the revelations about Iran's second uranium enrichment facility, the Russian president said his government might ultimately accept further sanctions as inevitable.

Since then, Mr Obama has met a key Russian demand to scrap plans to deploy interceptor missiles in Poland and a radar station in the Czech Republic as part of a US missile defence system in Europe.

The US administration insisted it did not expect concessions in return.

But US officials have called on Russia to support, or at least not oppose, the idea of the UN Security Council imposing tougher sanctions on Iran if it fails to live up to its international obligations.

The council wants Iran to end uranium enrichment and has approved three rounds of sanctions - including bans on Iran's arms exports and all trade in nuclear material.