His comments came as Mahmoud Ahmadinejad, the Iranian president, was due to arrive in China later on Thursday to tour the World Expo in Shanghai.

He is not expected to hold talks with senior Chinese leaders.

Intense lobbying

China had been a vocal opponent of a fourth round of sanctions against Iran for its nuclear programme.

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But it chose to vote for the sanctions on Wednesday instead of exercising its veto power as one of five permanent members of the council.

Its support came about only in recent months after intense lobbying by the US and its allies.

Victor Gao, the director at the China National Association of International Studies, a government think-tank, told Al Jazeera that China's decision to vote was mainly because the adopted resolution was a watered-down version that contains voluntary provisions.

"In this process China has repeatedly emphasised that 'diplomacy, engagement and dialogue' with Iran is a better solution, especially after Turkey and Brazil reached the agreement with Iran to swap nuclear materials," he said.

"Furthermore, the key provisions in this resolution are voluntary ... it basically creates a legal justification for countries who want to take those actions as specified in the resolution."

Diplomatic aim

Gao said China has been consistent in opposing nuclear proliferation but at the same time has maintained that other countries, including Iran, should have the right to the peaceful use of nuclear material.

He said China has firmly opposed the nuclear programmes in both Iran and North Korea.

"Even today China is calling North Korea to discontinue its nuclear programme. It does not want to see nuclear proliferation programme either on the Korean peninsula or in the Middle East," Gao said.

China, an ally of Iran and one of the Islamic republic's major trading partners in recent years, was long reluctant to sign on to the sanctions.

Li Baodong, the Chinese ambassador to the UN, was quoted as saying by the official Xinhua news agency: "The new resolution is aimed at bringing Iran back to the negotiating table and activate a new round of diplomatic efforts."