SINGAPORE - Deciding on the operating model for the Singapore-Kuala Lumpur high-speed rail (HSR), including how the project will be financed, will be high on the agenda for both countries.

One of the key considerations will be sustainability, Senior Minister of State for Finance and Transport Josephine Teo said on Saturday.

"We have to think about how it will operate long into the future," she said. "You have to make certain assumptions, like how many people could potentially use the high-speed rail and what is the frequency with which they will use it."

These principles will have to be laid down and Singapore will have to work closely with Malaysia to tackle these issues, Mrs Teo said at a community event in Toa Payoh.

The engineering design of the track section in Singapore and the terminus, which was recently announced to be on the site of the Jurong Country Club, will also have to be decided.

"From the point of view of Singapore, where the land is so scarce, it makes sense to put most of it underground," she said. "But underground facilities are also challenging in their own ways, not only from a construction standpoint but also in terms of how you eventually operate it. In addition to the fact that underground facilities are much more costly. We have to weigh the benefits as well as the costs of doing so."

The rail link, which will be between 320 and 340km, is expected to bring the journey between Singapore and KL to just 90 minutes. No firm deadline has been given for the project.