What about China?

The headlines in regards to Iran in recent days has been primarily focused on Russia. President Vladmir Putin recently made a historic visit to Iran to talk about nuclear plans, the Caspian Sea, among other mutual concerns. While some people were alarmed by the meetings many in the West still believe a deal can be made with Russia despite its nuclear relationship with Iran. It is believed that the US can try to cajole Russia to take a harder line with Iran at the Security Council. Russia on the outside appears to have friendly relations with Iran; but Russia does not want a regional hegemon at its doorstep, especially a nuclear one. US's Iranian policy is currently based on global economic sanctions. If the sanctions fail, it would most likely lead to war. The sanctions regime has been working but the US knows that the noose needs to be tighten. Russia could help it but at the same time will continue to be reluctant, in order to extract more concessions from the US. If the US succeeds with getting Russia on the table, the problem still won't be solved. China could always veto any UN resolution demanding more sanctions.

China's relationship with Iran is very close and they have access to Iranian oilfields . Iran is the 2nd largest supplier of oil to China -Washington Post China is the 4th largest economy and growing and its blossoming trade with Iran will be the major stumbling block that will ultimately restrict the complete tightening of the noose. Cajoling China will be a bit harder then with Russia.

Update The Washington Post reported yesterday on the issue of sanctions against Iran and how Iran is beginning to circumvent them due to increase in trade with China, and utilizing Asian banks and finding other economic opportunites away from the West. If the US cannot convince the world that Iran's nuclear ambitions is a threat than a war will be looming.