On the same day, President Hu Jintao and US President George W. Bush held a telephone conversation on the subject, in which the Chinese leader pledged to maintain the working of the international non-proliferation system. He told Mr Bush that Beijing was ready to play a constructive role in resuming negotiations as soon as possible.

The United States has been critical of China's expanding relations with countries that it considers to be 'pariah states', such as Iran, Sudan, Zimbabwe and Myanmar. Beijing's policy of friendship with those countries is largely driven by its interest in their crude oil and other natural resources.

Mr Bush is said to have cautioned his Chinese counterpart in April that countries are judged 'by the company they keep'.

The two nations may have agreed on last week's package, but there is little guarantee that they will continue to see eye to eye if the Iranians should baulk.

According to the proposals, sanctions would be imposed on Iran within the framework of the UN charter if Tehran refuses to co-operate. It is significant that China agreed to sanctions, but the proposals stop short of mentioning specific articles in the UN charter that could lead to possible military action - a course that China has previously opposed.

There is little doubt that Beijing and the US both want to prevent Iran from acquiring nuclear weapons.

Until now, however, China has insisted on using diplomatic means to resolve the issue, while the US wants to wield the stick as well as wave the carrot.

Iran is not the only issue on which China is seeking to accommodate the US. Beijing has also been more co-operative on Sudan, where several hundred thousand people in Darfur have been killed in actions described by the west as genocide.

Beijing agreed to sanctions against individuals in Sudan, although not against the government. Moreover, 430 Chinese peacekeeping personnel have arrived in Sudan to help monitor a truce in the region.

The Chinese government insists that it has a policy of not interfering in a country's internal affairs, regardless of its human rights practices. This stance has allowed it to sign agreements for the exploration and purchase of natural resources with countries ostracised by the west.

This policy of 'see no evil, hear no evil' is opposed by Washington. 'Because of China's rise, it cannot choose not to have an influence,' a senior Bush administration official said in an interview in Washington. 'It can use its influence in positive ways or by neglect.'

While China wants to protect its economic interests, it also wants to be seen as a strategic partner of the United States. This theme was repeatedly sounded by Mr Hu in the US in April.

After Mr Hu and Mr Bush talked in the White House, the Chinese leader declared that, 'a good China-US relationship is of strategic importance ... in the Asia-Pacific region and in the world at large'.

In the coming weeks, the world will be watching to see how far China is willing to go in subordinating its economic interests to further the loftier goal of maintaining the global non-proliferation system.

Frank Ching is a Hong Kong-based writer and commentator