The US has complained to Beijing about a new deal between Sinopec, the Chinese state-owned energy company, and Iran, in a sign of the rift between the world’s big powers about Tehran’s nuclear programme.

The contract to develop Iran’s Yadavaran oil and gas field, signed in Tehran on December 9, follows a 2004 memorandum of understanding and has been valued by Gholam Hossein Nozari, Iran’s oil minister, at $2bn.