When Mahathir was first prime minister, rows erupted frequently over everything from water - Singapore gets its water supply from Malaysia - to the Malaysian leader's plan to build a bridge connecting the neighbours to replace the current causeway.
"It's not beneficial. It's going to cost us a huge sum of money", Mahathir said.
Asked about this, a spokesman from Singapore's MOT said it is still awaiting "official communication from Malaysia".
This comes in response to Malaysian Prime Minister Tun Dr Mahathir Mohamad announcing in a press conference on Monday that Malaysia would pull out of the deal with Singapore.
Mahathir, who won a surprise election victory this month against Najib Razak's long-ruling coalition, is seeking to fix the country's finances, which he says deteriorated dramatically after the former government became embroiled in a huge financial scandal.
The unanticipated announcement came as both countries this week processed another major about-turn in policy affecting both countries - the new Malaysian government's decision to cancel a multibillion-dollar rail project linking Kuala Lumpur with the Lion City.
mStar reported that Dr Mahathir said, "We know some Malaysians want to help when they heard about the staggering debt we are facing and we welcome such patriotic efforts".
Last night Singapore's transport ministry said it had not received official confirmation of the Malaysian decision.
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The Facebook page of the powerful Sultan of Johor - Malaysia's southernmost state bordering Singapore - previous year published a video of a tiny maritime facility built on Middle Rock.
He said the decision to cancel the project was taken "to reduce the amount of borrowings" by Najib.
When questioned about the compensation that needed to be paid, he said he "supposed" it would be RM500mil. We will make no money at all from the operation.
Mahathir has reopened an investigation into 1MDB that was suppressed during Najib's rule.
"In reality, infrastructure projects such as the HSR bring returns and benefits in the form of property value growth, local economic stimulus, technology transfer, high-income job opportunities, the entry of talent from Singapore and tourism".
He had, in an earlier interview, cited the need to do away with unnecessary projects, one of them being the cross-border HSR, which will cost Malaysia RM110 billion (S$37 billion) and not earn them "a single cent".
However, Koh still hopes the HSR would link Kuala Lumpur and the republic and be extended to Malaysia's northern city of Penang.
An express service on the line was estimated to be launched by the end of 2026.