Juan Cole is Richard P. Mitchell Collegiate Professor of History at the University of Michigan.

The four rounds of United Nations Security Council sanctions on Iran are likely about as far as Russia and China are willing to go. Even the new charges against Iran apparently contained in the forthcoming International Atomic Energy Agency report (which do not rise to the level of accusing Tehran of having an active nuclear weapons program or of having diverted uranium to it), according to Reuters, are unlikely to impress China and Russia.

The problem is that sanctions on the Iranian financial and banking sector are already so extensive that the only way to go beyond them is to start a boycott of Iranian petroleum and gas.

But China simply won’t go along with any such policy. In fact, China increased its petroleum imports from Iran in the first half of 2011 by 50% over the previous year. China took 650,000 barrels a day from Iran last June, making the latter the third biggest supplier, following Saudi Arabia and Angola. China also increased its naphtha imports from Iran by 280% over the previous year!

China is now the world’s second-largest petroleum importer, after the United States, and clearly sees imports from Iran as an important part of its energy mix. So China is not voting at the U.N. to inflict on itself a shortfall of over half a million barrels a day of petroleum....