Iran's top nuclear negotiator warned the West to stop "threatening" Tehran as US President Barack Obama urged Chinese President Hu Jintao to cooperate in blocking Iran's atomic ambitions.

The harsh words from Saeed Jalili came as Western calls mount for tough new punitive action against Iran over its suspect nuclear programme -- action that hinges on the approval of China, which wields a UN Security Council veto.

Beijing has until now refused to back Western calls for new sanctions, and earlier in the day again urged all parties to hold more talks and "show flexibility" in resolving the international standoff over Iran's atomic drive.

In a phone call with Hu, Obama called for better Sino-US cooperation to ensure "that Iran lives up to its international obligations," the White House said.

Jalili suggested, however, that Beijing was heeding Tehran's calls for help.

"Many issues came up in our talks on which China accepted Iran's position," Jalili told reporters after talks with Chinese officials including Foreign Minister Yang Jiechi and State Councillor Dai Bingguo.

"We jointly emphasised during our talks that these sanctions tools have lost their effectiveness," Jalili said, though he said reporters "must ask China their position".

The Chinese foreign ministry did not immediately respond to an AFP request for comment.

The envoy said the West should change their "erroneous methods" and stop "threatening" Iran, warning that talks with six world powers including China and the United States could collapse if the West does not back off.

"If they continue with simultaneous talks and pressure, these negotiations cannot succeed," Jalili said.

"China as a large country can play an important role in changing these wrong methods."

The five permanent UN Security Council members -- Britain, China, France, Russia and the United States -- plus Germany have been involved in talks with Iran for months to try to end the standoff.

Beijing has a close diplomatic and trade relationship with Iran, dominated by its imports of Iranian energy resources -- a point emphasised by Jalili, who said: "We believe China and Iran's friendly relations will continue."

US Ambassador to the UN Susan Rice said China was ready for "serious negotiations" on Iran -- a move hailed by the White House as an "important step" -- but the language used in Beijing did not signal any policy shift.

Yang said China "urges relevant parties to step up diplomatic efforts, and show flexibility, to create the conditions to resolve the Iranian nuclear issue through dialogue and negotiation," the foreign ministry said Friday.

The day before, ministry spokesman Qin Gang told reporters China would continue to push for a peaceful settlement of the issue through "diplomatic means".

Russia has also been reluctant to agree new sanctions but has taken a harder line on Iran in recent weeks.

The United States and its allies suspect Iran is secretly trying to develop the atomic bomb, but Tehran says its nuclear drive is purely for civilian energy purposes, and that it has the right to nuclear technology.

When asked, Jalili indicated Iran had no new proposals it planned to bring to the negotiating table, saying Tehran's position was already clear.

Obama said earlier this week that he wants a fourth round of UN sanctions agreed upon within weeks, and later Friday said Washington will continue to crank up the pressure on Iran.

"I have said before that we don't take any options off the table, and we're going to continue to ratchet up the pressure and examine how they respond," he said in an interview with CBS television's "Early Show".

In his rare hour-long call with Hu late Thursday from Air Force One, Obama "underscored the importance of working together to ensure that Iran lives up to its international obligations," the White House said.

Beijing and Washington have been at odds for months over a host of issues, but China signalled a reduction in tensions when it said Thursday that Hu would attend a nuclear security summit in Washington on April 12-13.

earlier related report
Obama calls on Hu to support action on Iran
Washington (AFP) April 2, 2010 - US President Barack Obama called on Chinese President Hu Jintao to join forces on the Iranian nuclear standoff as he stepped up efforts to block Tehran's atomic program.

Obama "underscored the importance of working together to ensure that Iran lives up to its international obligations," the White House said following the rare hour-long telephone conversation late Thursday from Air Force One.

China has opposed new UN sanctions against Iran, which the United States and allies suspect is striving to develop a nuclear bomb.

Tehran insists its activities are peaceful and its top nuclear negotiator said after talks with Chinese officials in Beijing that the two sides agreed that sanctions had "lost their effectiveness".

The US leader welcomed Hu's attendance at an international nuclear security summit in Washington this month, which Obama said would be an "important opportunity for them to address their shared interest in stopping nuclear proliferation and protecting against nuclear terrorism."

The pair also discussed the importance of a "positive bilateral relationship," the White House said. The Chinese foreign ministry said Hu appealed for "healthy and stable" relations between the two nations.

Both sides must "respect each other's core interests and major concerns and properly handle differences and sensitive issues," Hu told Obama, according to the ministry.

Earlier Thursday, the Obama administration said it was pleased China agreed to join talks at the United Nations on toughening sanctions on Iran.

Spokesman Bill Burton said the move proved that despite lingering "disagreements we can work together on issues like nuclear proliferation."

The Obama-Hu phone call came as the two powers seek to overcome deep strains, including the valuation of China's currency, US arms sales to Taiwan and Tibet.

China has previously opposed the imposition of tough new UN sanctions on the Islamic republic, but said Thursday it was working for a "peaceful resolution" of the Iranian nuclear standoff.

Iran, which sent its top nuclear negotiator to Beijing, described the talk of new international action as an empty threat.

The presence of Tehran's chief nuclear negotiator Saeed Jalili in Beijing highlighted China's role in the tense UN Security Council debate on Iran's uranium enrichment.

Jalili said in Beijing that the West should stop "threatening" his country.

"Many issues came up in talks on which China accepted Iran's position," the Iranian envoy told reporters after talks with Chinese officials including Foreign Minister Yang Jiechi and State Councillor Dai Bingguo.

"We jointly emphasised during our talks that these sanctions tools have lost their effectiveness," Jalili said.

Obama said Tuesday he wants a fourth round of UN sanctions agreed upon within weeks.

China, which has a close diplomatic and trade relationship with Iran, and is one of five veto-wielding members of the Security Council, has repeatedly called for a negotiated settlement rather than new punitive action.

Hu's attendance at the nuclear security summit on April 12-13 and his lengthy conversation with Obama, appeared to mark a slight easing of tensions.

Chief among bilateral irritants is the value of the Chinese yuan, with some 130 US lawmakers calling on Treasury Secretary Timothy Geithner to accuse Beijing of manipulating its exchange rate for trade advantage -- and threatening legislation if he does not.

Tensions have also risen over US arms sales to Taiwan and Beijing's angry protests earlier this year over Obama's meeting with Tibet's exiled spiritual leader the Dalai Lama.

Hu stressed to Obama that "Taiwan and Tibet issues concern China's sovereignty, territorial integrity, and China's core interests, and properly dealing with these issues is key to ensuring the healthy and stable development of Sino-US relations," Chinese officials said.

Other disputes include human rights, climate change and Internet freedom after Google reported cyberattacks by China.