Singapore and Malaysia moved into the next stage of the high-speed rail project, which involves getting a feel of interest levels and views of prospective players who have the expertise or desire to build the link.

A request for information (RFI) was jointly issued by both governments yesterday. This market-sensing exercise will help gauge market interest and gather industry opinion on the commercial and technical aspects of the project, the Land Transport Authority (LTA) and Malaysia's Land Public Transport Commission said.

"The feedback received will inform the ongoing bilateral discussions and formal tender process subsequently," both parties said.

In a blog post, Transport Minister Khaw Boon Wan said the joint project is "still on track" but also pointed out the challenges. "It is a large, complex infrastructure project, and there are many examples of countries that have failed in their HSR (high-speed rail) aspirations or their HSRs have run into serious financial problems."

Mr Khaw said this is due to a "gulf" between the countries' ambitions and the market realities.

"To be sustainable and exemplary, the project must meet the market test," he said, calling the RFI a necessary "building block".

Before the calling of the RFI, Singapore and Malaysia carried out their own feasibility studies. The RFI exercise is expected to finish by the end of the year. The Singapore-Kuala Lumpur HSR was first announced by Prime Minister Lee Hsien Loong and his Malaysian counterpart Najib Razak in 2013.

While the HSR was targeted for completion by 2020, both prime ministers have said that this timeline will need to be reviewed.

According to LTA's website, the RFI is open to companies or consortiums interested in participating in the project in the areas of design, funding, construction, operations and maintenance.