Russia on Friday warned Iran it was missing out on a chance to start a broad dialogue, as US Secretary of State Hillary Clinton again sought to win the Kremlin's assent for tougher stance on Tehran.

Iran's defiance over its nuclear programme means the country is wasting a chance for talks to find a solution, Foreign Minister Sergei Lavrov said alongside Clinton after her talks with President Dmitry Medvedev.

"It is letting an opportunity to establish dialogue with the international community slip away," Lavrov said.

Later in talks with Clinton, Prime Minister Vladimir Putin, believed to have a final say on all issues related to Iran, stressed that sanctions would be counterproductive, his spokesman Yuri Ushakov said.

"A resolution (on sanctions) is possible," Putin said at the meeting. "But sanctions will not contribute in resolving the problem, they could be counterproductive," Ushakov quoted him as saying.

Clinton said Washington was now seeking support for "smart sanctions" against Tehran, a line that recalled the Kremlin's policy that any measures against Iran needed to be intelligent and targeted.

"We pursued the diplomatic track and thought it was correct to do so," she told reporters.

"We... are working very hard in the Security Council to obtain a resolution expressing the international community's disapproval of Iranian actions and pulling together... a regime of smart sanctions as President Medvedev has referred to them," she added.

Lavrov's comments were the latest indication of Russian frustration that Iran has failed to agree a deal with the international community to end the standoff over its nuclear programme.

Lavrov however reiterated Russia's traditional stance that sanctions against Tehran could be inevitable but did not make any public promises beyond that.

Lavrov said Medvedev told Clinton during her second and final day in Moscow that the sanctions against Iran should be "smart, non-aggressive and non-paralysing."

"As Russian President Dmitry Medvedev said, sanctions rarely work but there may appear a situation when they may end up being inevitable," Lavrov told reporters.

"And we don't rule out that such a situation may appear with respect to Iran."

Russia -- a veto-wielding permanent UN Security Council member -- traditionally has strong ties with Iran but Medvedev has repeatedly said sanctions against Tehran cannot be ruled out if necessary.

Medvedev called for targeted sanctions against Iran on a visit to Paris earlier this month, saying they should be "smart" and not target the civilian population.

On Thursday, the United States and Russia clashed over the launch of Iran's first nuclear plant Russia is building, with Putin saying the nuclear power facility would finally come online this summer.

That remark immediately drew Clinton's criticism, who said that move would send Tehran the wrong message.

Tehran is accused by the West of planning to build a nuclear bomb although it insists its nuclear drive is purely peaceful in nature.

Following Thursday's disagreement, officials sought to gloss over the differences, with Lavrov praising Clinton's visit which he described as "in-flight refueling."

Lavrov said that Medvedev noted that the two countries had "managed to implement a real reset" over the past year.

"We have managed to secure an unprecedented intensity of contacts at all levels," Russian news agencies quoted Lavrov as saying.