A year ago it would have been unthinkable. After all it was a city where driving to work became a life or death decision and where residents were cooped in enclaves amid murder and mayhem.

But yesterday the mayor of Baghdad surprised everyone by announcing plans for an underground train network that will literally carve a swathe through the city's sectarian lines.

If investors sign up, the world's most violent capital will soon have a $3bn (£2bn) metro. Sabir al-Issawi, Baghdad's mayor, said money had been set aside in next year's budget for a feasibility study.

Not the first time this has been proposed for Baghdad.

A train line under Baghdad was first flagged under Saddam Hussein during the 1970s, but shelved owing to three decades of war, blockades and invasion...

The project's engineer Atta Nabil Hussain Auni Atta, of Iraq's transport ministry, said old 1970s blueprints for the underground line were being redrawn to bring it up to speed with the specifications of modern railways.

"This is one of Baghdad's most important projects and we hope that investors will join it," he said. "We have called for tenders from them and we have some money to contribute from the government. We are planning to start work as early as next year.