The EastWest Institute on Tuesday published a joint US-Russian assessment of the threat from Iranian nuclear weapons and missiles which concluded that Tehran would need at least six years to develop a nuclear warhead that could be placed on a missile.

A group of 12 prominent Russian and US scientists concluded that Iran would need six to eight years to develop a ballistic missile that could carry a 1,000kg payload 2,000km. The unprecedented study was commissioned as tensions between Washington and Moscow grew amid George W. Bush’s plan to install a missile defence shield in Europe. Retired General James Jones, now the US national security adviser, was one of the leading proponents of the study before he entered government.