Singapore has insisted that the water agreements signed between Malaysia and the city-state in the 1960s must be fully complied with.

This was after Prime Minister Dr Mahathir Mohamad, in an interview with Channel News Asia, said he is looking to renegotiate the terms of the agreements which he had described as "ridiculous".

"The 1962 Water Agreement is a fundamental agreement that was guaranteed by both governments in the 1965 Separation Agreement which was registered with the UN.

"Both sides must comply fully with all the provisions of these agreements," Singapore's Ministry of Foreign Affairs was quoted as saying by Channel News Asia.

In the interview, Mahathir said it was "manifestly ridiculous" that Malaysia sold water to Singapore at three sen per thousand gallons.

That was okay way back in the 1990s or 1930s. But now what can you buy with 3 sen? Nothing.

"We are studying the case properly and we’ll make a presentation," he was quoted as saying.

Under the agreement, the generous sale is in exchange for Malaysia to purchase back a portion of the water at 50 sen per 1,000 gallons after it is treated.

The agreement is valid until 2061.