I agree with Dr Quek Koh Choon that it was very odd that Malaysian Prime Minister Mahathir Mohamad has flipped from calling the water deal from "unfair" to "immoral" (How is it 'immoral' to keep to an agreement?, March 2).

In recent times, Tun Dr Mahathir seems to share the same unpredictability of US President Donald Trump.

Last year, he said that Singapore and Malaysia were like twins "which come together and are separated, and still work together and help each other" (Malaysia and Singapore are like twins: Mahathir, Nov 13, 2018).

However, just a little while later, he turned adversarial about the price of three sen per 1,000 gallons of raw water.

The water price was based on circumstances in 1962, when both nations were starting out at the same level.

Malaysia's choice not to review the water price in 1987 was based on the consensus that raising the raw water price would mean doing the same for the treated water price to Johor.

Hence the 1962 Water Agreement should be upheld as sacrosanct.

Furthermore, the water issue was amicably enhanced when Singapore and Johor signed an agreement in 1990 to construct the Linggiu Dam, as a supplement to the 1962 agreement.

Before Dr Mahathir raises the water issue again, he should not forget that Singapore has spent more than $1 billion on various water projects in Johor.

There is, hence, no merit in raising the water issue once again.

Paul Chan Poh Hoi