In June, China National Petroleum signed a $5 billion deal to develop the South Pars gas field in Iran. In July, Iran invited Chinese companies to join a $42.8 billion project to build seven oil refineries and a 1,019-mile trans-Iran pipeline. In August,  another deal for $3 billion for China to help Iran expand two oil refineries.

China doen’t see Iran in the same way as we do. China’s economic links to Tehran are growing rapidly, and China’s leaders see Iran not as a threat but as a potential ally. Nor would the Chinese be distressed, the reasoning goes, should a nuclear-armed Iran sap American influence in the region and drain the Pentagon’s resources in more Middle East maneuvering.

China relies heavily on Iran’s vast energy reserves — perhaps 15 percent of the world’s natural gas deposits and a tenth of its oil — to offset its own shortages. The Chinese are estimated to have $120 billion committed to Iranian gas and oil projects, and China has been Iran’s biggest oil export market for the past five years. In return, Iran has loaded up on imported Chinese machine tools, factory equipment, locomotives and other heavy goods, building China into one of its largest trading partners.

China scholars say that the relationship is anything but one-sided. Iran has skillfully parceled out its oil and gas reserves to Chinese companies, holding exploration and development as a sort of insurance policy to retain Chinese diplomatic backing in the United Nations.

Beijing agreed to measures at the United Nations only after stronger American proposals had been watered down, and after Russia, the Council’s other critic of stiff sanctions, and a close ally of Iran, had signed off.

One noted Chinese analyst, Shi Yinhong of People’s University in Beijing, said in a telephone interview that China would probably follow much the same course should a new sanctions proposal reach the Security Council.

“China will do its utmost to find a balance” between Iran and the United States, Mr. Shi said. If Russia joins the other Council members in supporting a new sanctions resolution, he said, “China will do its best to try to dilute it, to make it limited, rather than veto it.”

But it is unlikely to do so happily. Supporting stronger sanctions might elevate China’s image as a global diplomatic leader, but the United States, not China, would reap the real benefits.

“China is not anxious to jump on this American train,” said one Chinese analyst, who spoke on the condition of anonymity in order to freely assess China’s foreign policy.