Royal Dutch Shell will repay a $2bn (€1.7bn) debt to the National Iranian Oil Company when sanctions on Iran are lifted and will consider investing in the country’s vast energy sector, Shell’s boss for new business said.

The EU has imposed a new range of sanctions on Iran intended to hit the country’s treasury and increase pressure on its Islamic regime over its nuclear programme.

Iran has halted its limited oil sales to France and Britain in retaliation for a phased EU ban on Iranian oil that is yet to take full effect, the oil ministry said yesterday.

Iran said it was very optimistic over a visit by UN nuclear inspectors aimed at shedding light on suspected military aspects of Tehran’s atomic work, but suggested Tehran would curb cooperation if the experts became a “tool” for outside powers.

Iran has today played down the impact of new Western sanctions targeting its vital oil sector.