Emeritus Senior Minister Goh Chok Tong said his Facebook post last week on the urgency of picking Singapore's next prime minister was made "on purpose to elicit a response" from the country's fourth-generation (4G) leadership.

"Having achieved my purpose, I'm not going to go further than that," said Mr Goh yesterday, referring to a rare joint statement that 16 younger ministers from the ruling People's Action Party (PAP) issued last Thursday.

The 16 office-holders said they were keenly aware that leadership succession is a pressing issue, and would pick a leader among themselves "in good time".

This came after Mr Goh's post on New Year's Eve, in which he highlighted the urgent challenge of choosing Singapore's next leader and said he hoped the current cohort would do so in six to nine months.

Prime Minister Lee Hsien Loong can then formally designate their choice as his potential successor before the end of this year, he added. "Whoever is chosen, the team will have to work together, bring in others, and gel to form a cohesive fourth-generation Cabinet," he wrote.

Asked about the joint statement, which did not specify a timeframe, Mr Goh said: "It can be earlier, it can be later... I'm not going to question them on what does 'good time' mean."

"But the point is, they've responded to the call that they have to decide very quickly," he told reporters at a youth awards ceremony in his Marine Parade constituency.

Mr Goh said: "Otherwise, in our nature, we normally don't want to fight for the post. And they're not fighting for the post, but they have to decide who should lead them. That's the difference in politics between us and other countries."

"(In) other countries they elbow one another," he added. "But we all do not have sharp elbows to get into that senior position. So I thought I should just signal to them to better decide."

Asked why he described political succession as an urgent challenge, Mr Goh replied that the answer "is very clear".

His Facebook post was the first time a senior figure from the PAP has publicly stated a timeline.

PM Lee has said he intends to hand over the reins of government to a successor by the time he turns 70, in 2022.

The statement by the 4G leaders was signed in alphabetical order by the group, and for the first time gave an indication of those in the cohort that will decide the next prime minister.