SINGAPORE - The Land Transport Authority has called tenders for the design and construction of tunnels and associated facilities for Singapore's end of the high-speed rail project connecting with Kuala Lumpur.

Construction is expected to start next year.

"We called the tenders for the design and construction of twin bored tunnels and associated facilities on April 6, and the design and construction of cut and cover tunnels leading into the Jurong East terminus on April 11," an LTA spokesman said.

The tunnels are constructed using tunnel-boring machines, which are preferred for longer stretches of underground excavation as they cause less disturbance to surface utilities, buildings and structures.

In comparison, cut and cover tunnels are constructed using retaining structures, then excavating in stages.

This method is preferred for shorter distances and in open areas with fewer surface utilities, buildings and structures.

Cut and cover tunnels are also more suitable for larger underground structures, such as the tunnel leading to the Jurong East terminus.

The LTA said the remaining civil tenders will be called in the coming months, and construction work is expected to commence next year.

"We remain on track to commence the Kuala Lumpur-Singapore express service by 2026," the spokesman said.