The Land Transport Authority has called a tender for a contractor to take over a Downtown MRT Line project from a company which went bankrupt.
It expects to appoint one by next month, in a bid to minimise delay to the project.
Six companies have been shortlisted: McConnell Dowell SEA, Penta-Ocean Construction, Nishimatsu Construction, Samsung C&T Corp, Shanghai Tunnel Engineering and SKEC (Singapore).
The successful bidder will take over from Austrian builder Alpine Bau, which was working on the line's King Albert Park, Sixth Avenue and Tan Kah Kee stations when it filed for insolvency and stopped work in mid-June.
The project is part of 10 civil contracts for the 16.6km, 12-station line, which joins Singapore's north-western corridor to the new Marina downtown.
It was originally scheduled to be running by 2015, but Transport Minister Lui Tuck Yew told Parliament last month that there would be a delay, and costs would rise.
Industry watchers said the cost increase was expected, as a new contractor will have to assume unknown risks when it takes on a project that was partially completed by another party.
Experts also said chances of mitigating any delay were slim.
Associate Professor Chan Weng Tat of the National University of Singapore's Department of Civil and Environmental Engineering said much depended on "the smoothness of the handover".
But he acknowledged that a four-month work suspension, which is already a conservative estimate, would be "a bit tough to make up".
He noted that making up for a delay midway through a project was doubly hard.
"If it had been at the early stages... it would have been easier," said the professor, whose expertise includes project management. "The question now is how much knock-on effect will this have on the rest of the project."
The LTA has, meanwhile, appointed McConnell Dowell as caretaker contractor for the suspended stretch. The Australian company is working on a Downtown Line project immediately north of the affected portion.
An LTA spokesman said that the caretaker will maintain safety and security of the site, provide pest control and ensure that equipment remains in working condition.
"Our immediate priority is to appoint contractors that are able to resume work at the earliest possible (time) as there could be safety issues when tunnel-boring machines remain stationary underground for long periods of time," she added.