Prime Minister Lee Hsien Loong has given the clearest hint of proposed changes to the law to guarantee that ethnic minorities are elected president from time to time.

This special provision may need to be used, he said, only if there has not been a president of a particular race for a long time - say four, five or six terms.

Then the next election could be reserved for a member of that community if a qualified candidate presents himself or herself.

"You want a mechanism where, if you've had a long gap, then the next election - if you have a qualified minority candidate - is held only amongst a minority group," Mr Lee said in an interview on race and politics with MediaCorp broadcast last night. "And so you will be able to get a Malay or an Indian president."

But if, for some reason, no qualified minority candidate presented himself or herself, then an open election would be held and "whoever wins, wins", he said.

Mr Lee was answering a question on how proposals by a Constitutional Commission to ensure minorities can be elected president, set to be published this week, would work.

There has not been a Malay president since Mr Yusof Ishak held the post from 1965 to 1970, and observers think next year's election could be reserved for a Malay candidate.

At the National Day Rally two weeks ago, Mr Lee spoke on the need for presidents from all races so minorities feel assured of their place in society. But he took ill and had to cut short his remarks.

In the interview aired yesterday, he said minority candidates will find it hard to be elected under the current system, and the proposed changes are not tokenism, but the right step for Singapore's future.

"It is a very necessary symbolism of what we are as a multiracial society - what Singapore means, stands for and what we aspire to be."

Mr Lee noted that some of the ideas raised before the nine-member panel included rotating the presidency between the different communities, and having a team of candidates from different races.

But he felt the "least intrusive and most light-touch" way was to reserve the election for the under-represented group, but with the provision applying only when needed.

After the panel's report is out, the Government will respond with a White Paper outlining its proposals, before moving amendments to the Constitution. Changes should be in place before next year's presidential election, Mr Lee added.

The changes will also raise the qualifying criteria for candidates from the private sector above the current benchmarks to keep pace with an economy that has grown seven times since the elected presidency was introduced in 1991.

Mr Lee said he had seen how the system worked over 25 years. Former president S R Nathan was elected unopposed twice, but it was hard to say how an election would have been when he first stood.

He also did not think a minority candidate would have a fair chance in a tense election like that in 2011.

Acknowledging that there might be some reservations about the changes, he said he had a responsibility to make them as he was familiar with the system, and should not leave the issue to his successor.

"This is something which needs to be done... I will persuade you that it is something that we should do and which is good for Singapore.