Singapore has reiterated that all parties to the water supply agreement with Malaysia must adhere to its terms, after the Johor state government announced last week plans to produce its own treated water.

The southern Malaysian state supplies raw water to Singapore and relies on Singapore for its supply of treated water.

"Singapore notes the Johor state government's plans to increase its capacity to produce treated water to meet its own needs," Singapore's Ministry of Foreign Affairs said in a statement last night. "This does not affect Singapore's position that all parties, including Johor, must honour the terms of the 1962 Water Agreement, which no party can unilaterally change."

The ministry's comments were in response to Johor Menteri Besar Osman Sapian's statement that the state plans to be self-sufficient in treated water instead of relying on Singapore. "We have a plan to be self-sufficient but that is still in the planning stage and cannot be divulged at the moment," Datuk Osman said last Friday, a day after Prime Minister Mahathir Mohamad urged Johoreans to speak up on the "morally wrong" water deal between Malaysia and Singapore.

Under the 1962 Water Agreement, which expires in 2061, Singapore is entitled to draw up to 250 million gallons a day (mgd) of raw water from the Johor River at three sen per 1,000 gallons. Johor is entitled to buy five mgd of treated water from Singapore at 50 sen per 1,000 gallons. Singapore has said this price is heavily subsidised and below the cost of treating the water.

Singapore has, in practice, been supplying 16mgd of treated water to Johor at the state's request.