Russia on Tuesday urged the West to consider relaxing sanctions against Iran, saying there was unprecedented hope of a breakthrough in the nuclear standoff as Tehran was ready to make a major concession on uranium enrichment.

Foreign Minister Sergei Lavrov said Iran was now ready to agree to suspend efforts to enrich uranium to 20 percent. If realised, such a move would mark Tehran's biggest compromise for years in the crisis.

Lavrov's comments added to the cautious optimism days after the election of moderate cleric Hassan Rowhani as Iran's new president to replace the hardline populist incumbent Mahmoud Ahmadinejad.

"It is necessary to avoid tightening the sanctions pressure against Tehran and start thinking about ways for a possible weakening (of sanctions) in a way that is tangible for Iran," Lavrov said in an interview with Kuwaiti news agency KUNA.

Iran and world powers have held two rounds of talks in Almaty in Kazakhstan which have been marked by a better atmosphere than previous talks.

"For the first time in many years, hopeful signs have appeared in this process," Lavrov said in the interview, a full transcript of which was published by the foreign ministry at the same time as world leaders were discussing Iran at the G8 summit.

"The Iranians are confirming the main thing -- which is a readiness even at the current stage to stop enriching uranium to up to 20 percent," Lavrov said.

Uranium enrichment is the crux of the decade long standoff over the Iranian nuclear programme as the process can be used to make both nuclear fuel and the explosive core of an atomic bomb.

Iran insists its nuclear programme is solely civilian in nature but its assertions do not convince the West and Israel, which accuse Tehran of seeking the bomb.

A possible concession on enrichment had been hinted at by Iran's chief nuclear negotiator Saeed Jalili after talks in Almaty in April. He said Iran could "review" a suspension of 20 percent enrichment, while insisting also on its rights to the full fuel cycle.

"This could be a breakthrough agreement and to a large extent remove the acuteness of the existing problems," said Lavrov, saying concessions by Iran needed to be met with similar steps by world powers.

"The international community needs to react adequately to constructive moves by Iran, including the gradual removal of both unilateral and UN Security Council sanctions," he said.

"It would be unforgivable not to use this opportunity," Lavrov added.

It remains to be seen how the Western powers will respond to Lavrov's calls. However US President Barack Obama said Monday that Tehran had to understand that the most strict economic sanctions would stay in place without clear steps from Iran demonstrating it was not developing the bomb.

"Our bottom lines have been, show the international community that you're abiding by international treaties and obligations, that you're not developing a nuclear weapon," Obama said.

Iran has been slapped with successive rounds of UN Security Council sanctions and also unilateral measures by the United States and the European Union.

The sanctions initially only targeted the nuclear and defence industries but have now started to hurt the wider economy, causing concern among ordinary Iranians and even the leadership.

In a separate statement, the Russian foreign ministry welcomed what it said where vows by Rowhani to show the greatest transparency over the Iranian nuclear programme.

It urged the holding of the next round of talks between Iran and world powers as soon as possible "especially as a considerable basis for moving towards the first decisions in the negotiations has already been made".

Analysts have however cautioned against seeing a major turnaround in Iran's position, given that foreign and security policy is still controlled by the Iranian number one, Supreme Leader Ayatollah Ali Khamenei.