President Mahmoud Ahmadinejad visits the Shanghai Expo on Friday for "Iran Day" after one of his top officials delivered an extraordinary rebuke to Beijing for backing sanctions against Tehran.

The visit, in which Ahmadinejad will tour the Iran pavilion at the glitzy World Expo and give a news conference, reflects delicate ties with China.

Although China has close economic and energy ties with the Islamic republic, this week it joined its UN Security Council partners in backing fresh sanctions against Tehran for its nuclear programme.

While Ahmadinejad is being welcomed in Shanghai, he is being kept at arms' length by China's top leaders, observers have noted.

President Hu Jintao is away attending a meeting of the Shanghai Cooperation Organisation in Tashkent.

Iran has observer status in the regional security forum and Ahmadinejad has attended its meetings before but is staying away this time, reflecting Iranian displeasure at the decision of both China and Russia to back the UN sanctions.

The UN Security Council adopted a US-drafted resolution hitting Tehran with new military and financial sanctions on Wednesday.

"These resolutions are not worth a dime for the Iranian nation," Ahmadinejad said on a visit to Tajikistan that day.

China has retained close economic ties to Iran despite Western censure of the country's nuclear programme, which world powers suspect is aimed at developing a nuclear weapon, something Tehran denies.

Some observers consider China has taken advantage of Iran's relative isolation to gain a greater foothold in the Islamic republic, particularly in the oil and gas sector.

But on Thursday Iran's atomic chief Ali Akbar Salehi, who oversees the country's nuclear programme, lashed out at China.

"China is gradually losing its respectable position in the Islamic world and by the time it wakes up, it will be too late," he said, according to ISNA news agency.

China for its part was taking pains to reassure Iran of its long-term friendship.

"China highly values relations with Iran and feels they are conducive to regional peace, stability and development," foreign ministry spokesman Qin Gang said in Beijing.

Qin reiterated that the goal of the new resolution, the fourth round of UN punitive measures targeting Tehran, was to bring Iran back to the negotiating table, not to shut the door on dialogue.

In Tehran, officials threatened on Thursday to downgrade ties with the UN watchdog the International Atomic Energy Agency in response to the new sanctions.

"The majlis (parliament)... will adopt on Sunday a top priority bill which talks of decreasing ties with the IAEA," Esmaeel Kosari, a member of its committee on national security and foreign policy, told Fars news agency.

Ahmadinejad is due to visit the Iran and China pavilions at the World Expo, where Iran Day will be celebrated, before giving a press conference at 3:30 pm (0730 GMT), according to Iranian Expo officials.

earlier related report
Shanghai group mulls expansion as Iran snubs gathering
Tashkent (AFP) June 10, 2010 - Russian President Dmitry Medvedev arrived in ex-Soviet Uzbekistan on Thursday for an annual meeting of a regional security group and talks with leaders including Chinese President Hu Jintao.

The Shanghai Cooperation Organization, where heavyweights Russia and China play a major role, meets on Thursday and Friday seeking to lift a moratorium on expansion and open its doors to new members, officials said.

The Kremlin's top foreign policy aide Sergei Prikhodko said the summit would take place amid "an escalation of a number of problems," including new tensions on the Korean peninsula and Iran's defiance in the face of new sanctions.

The six-nation group includes four ex-Soviet Central Asian states -- Kazakhstan, Kyrgyzstan, Tajikistan and Uzbekistan, while Iran, India and Pakistan have observer status and have in the past expressed interest in joining.

A major outcome of the two-day summit in Uzbekistan is expected to be the adoption of a blueprint for expanding membership, Prikhodko said.

He refused to say which country has the best chance to join the SCO in the near future, simply noting a number of countries have expressed keen interest.

"Iran wants to be in, Pakistan wants to be in, Afghanistan wants to be in," Prikhodko told reporters ahead of the summit.

But while Afghanistan's Hamid Karzai and Pakistan's Asif Ali Zardari are both expected to attend, President Mahmoud Ahmadinejad of Iran, whose country was slapped with fresh UN sanctions over its nuclear programme on Wednesday, will conspicuously be absent.

By contrast, he chose last June's SCO meeting in Russia for his first foreign trip since his disputed re-election victory.

Since then, ties between Russia and Iran have dramatically worsened as Medvedev called Iran's behaviour "irresponsible" and signaled that Russia would support fresh sanctions against the Islamic republic.

Ahmadinejad is planning to stay away from the two-day summit, even though he visited neighboring Tajikistan on Wednesday.

On Thursday he will head to China for a visit to the Shanghai Expo, an Iranian diplomat said.

In any case, Iran would not be the first candidate to win membership, analysts say.

"Iran -- with its relations with Russia, its relations with America and its nuclear drive -- is not the best candidate for the SCO," said Alexei Malashenko, a Central Asia expert at the Carnegie Moscow Center.

Malashenko said the configuration of the regional grouping is unlikely to change dramatically in the near future even though they may be open to the idea of expansion.

"It would be naive to speak of any expansion without China's permission," he told AFP. "And I have not heard of their readiness" to welcome new countries, he said.

The SCO was set up in 2001 as a security counterweight to NATO that would allow Russia and China to rival US influence in Asia but is increasingly looking to cooperate on economic brass tacks, analysts say.

"The longer the European Union puts its relations with Russia on hold, the more actively the SCO will work," said Vladimir Zharikhin, deputy director of the Institute of CIS Countries.

The summit is also expected to adopt a political declaration mapping out the member countries' future cooperation, the Kremlin said.

Instability in Afghanistan and fragile Kyrgyzstan, where bloody protests toppled President Kurmanbek Bakiyev in April, are also expected to top the agenda.

Besides a scheduled bilateral meeting with Hu, on Thursday Medvedev will meet Uzbekistan's leader Islam Karimov, Pakistan's Zardari and Kazakh leader Nursultan Nazarbayev.

On Friday, Medvedev will separately meet for talks with Afghanistan President Hamid Karzai.