Last year it was given full membership of the Shanghai Co-operation Organisation, a Eurasian security and economic club dominated by China and Russia. In January Iran was admitted to BRICS, another group that China and Russia are trying to nurture as a bastion of West-sceptics.

Crude benchmarks slumped on Tuesday as traders fretted about weak Chinese demand and weighed up a report saying that Israel won't attack Iranian oil targets.

Iran exports nearly half of its oil production and uses the rest for its own domestic needs. The sliver of Iran’s oil exports that China does not purchase is shipped mainly as economic assistance or barter to two nearly bankrupt allies, Syria and Venezuela, that have little money to pay for fuel.