Kuwait is building one of the world's longest causeways to its remote north where it will pump billions into "Silk City", aiming to revive the ancient Silk Road trade route.

The oil-rich emirate is eager to inject life into the uninhabited Subbiya region on its northern tip that has been chosen as the location for Silk City.

The plan is to reinvigorate the ancient Silk Road trade route by establishing a major free trade zone linking the Gulf to central Asia and Europe.

The 36-kilometre bridge, three-quarters of it over water, will cut the driving time between Kuwait City and Subbiya to 20-25 minutes from 90 minutes now.

Investment in the Silk City project is expected to top $100 billion, and a 5,000-megawatt power plant has already been built in Subbiya.

At a cost of 904 million dinars ($3.0 billion), the Sheikh Jaber Al-Ahmad Al-Sabah Causeway, named after the emir who died in January 2006, is one of the largest infrastructure ventures in the region.

It is already nearly three-quarters completed.

Despite the sharp drop in oil income which made up 95 percent of public revenues, the emirate has pledged to keep spending on capital projects almost intact.

Kuwait boasts a $600-billion sovereign wealth fund, and is in the middle of a five-year development plan stipulating investments worth $115 billion.

"The causeway project is a strategic link connecting Kuwait City to the northern region," said Ahmad al-Hassan, assistant undersecretary for road engineering at the public works ministry.

He told AFP that in addition to the fully integrated residential Silk City, other economic ventures are planned for Subbiya and its surroundings.

A large container port is also under construction on nearby Bubiyan, Kuwait's largest island.

Completing the causeway and harbour projects will pave the way for transforming the area into a commercial and investment hub with a free trade zone planned on five small islands nearby.