Extending the minimum occupation period, shortening leases or even going back to the time when buyers can sell HDB flats only back to the Housing Board are some suggestions being looked into to bring down new flat prices.

Minister for National Development Khaw Boon Wan said these are "reasonable suggestions" which he will "discuss through".

At the heart of the transition is the impact of "trade-offs" between homeowners and home-buyers, who may have differing views and needs. "How do we make sensible trade-offs which are sustainable?" he asked at a community event in Woodlands today.

"Most people actually do not have a housing problem. But a minority do, and they are serious housing problems," he said. "So we need to tackle them, but in a way that is not at the expense of homeowners."

Mr Khaw added that the criteria for singles to buy flats directly from HDB announced on Friday may be expanded, depending on whether the demand is manageable. Later this year, singles aged 35 and over will be able to buy two-room flats directly from HDB if their monthly salary does not exceed $5,000.