Construction work on the 40km causeway linking Qatar and Bahrain will begin in the first quarter of 2010, the official in charge of the project said.

The road, known as the Friendship Bridge, is thought to be the world’s longest marine causeway.

The structure will include a two-lane dual carriageway with 17km of embankments, 23km of viaducts and bridges and two bowstring arch bridges reaching up to 40m above shipping channels.

The road-cum-rail bridge will also include freight and passenger rail lines.

The project is expected to cost between $3bn and $4bn and will be funded by the two countries.

Work will be carried out by France’s Vinci and Germany’s Hochtief and is expected to finish in 2015.