Singaporeans will have to wait a little longer to find out who their next prime minister is.

Prime Minister Lee Hsien Loong said yesterday that no new deputy prime ministers will be appointed during the Cabinet reshuffle, which he said would take place after this year's Budget in February.

This suggests there will be no clear front runners made known to the public even after the reshuffle.

"My assessment is, it probably will take a little bit longer," he added when asked about a timeline suggested by Emeritus Senior Minister Goh Chok Tong last month.

Mr Goh had said he hoped the younger ministers will choose their leader in the first six to nine months of this year, and that this person can be made PM-designate within 2018.

PM Lee said: "ESM (Goh) is speaking with the privilege of watching things rather than being responsible to make it happen. I think we know it is a very serious matter."

He added: "The team is taking shape. The dynamics among them, they are working it out. They are learning to work together.

"Also, they need a bit of time for Singaporeans to get a feel of them - not just to be known as public figures, but to be responsible for significant policies... carrying them, justifying them, defending them, adapting them, making them work, and showing that they deserve to lead.

"I would not be able to say for certain that it will be settled within the next six to nine months, but it will have to be done in good time. I am confident it will be."

The Cabinet reshuffle will be "a significant step in exposing and building the new team, and putting them into different portfolios", he said.

Designating a successor will depend on the team's dynamics.

"I would not say that that is imminent," he said. "If it is settled, everybody will know."

PM Lee also took stock of his visits to Sri Lanka and India when he spoke to the Singapore media in New Delhi. He returns to Singapore today.

The race to be Singapore's next PM is generally viewed by observers as having narrowed to three candidates: Finance Minister Heng Swee Keat, Minister in the Prime Minister's Office Chan Chun Sing and Minister for Education (Higher Education and Skills) Ong Ye Kung.

On whether these are indeed the front runners, PM Lee said: "I think they are all good ministers."

Asked who he thinks is best suited for the job of PM, he replied: "I think there is a strong team."

He added that many people see the leadership as being "personalised as one person".

"Actually, there is a team. The team works together and they have one - Mr Lee Kuan Yew said - striker. Now, you have to strike from time to time, but you are really also sometimes spokesman on behalf of the team, bringing together a collective wisdom and giving voice to that.

"In the next team, that aspect of it will have to be even more important," he said.

As for whether he will give the younger ministers his views on their relative strengths, PM Lee said: "If they ask me my views, I will try my best to be helpful."

He noted that founding prime minister Lee Kuan Yew had, from time to time, publicly given his views on the younger members of his team and their strengths, which they found "a little bit awkward to be put under the spotlight".

"I don't think I need to do that to my younger ministers," he said.

PM Lee's remarks come less than a month after 16 younger leaders from the People's Action Party issued a statement, in response to ESM Goh, to say that they will choose a leader from among themselves "in good time".

Commenting on the statement, PM Lee cast doubt on the idea that it is an exhaustive list of the fourth generation leadership team.

He noted that "a lot was made" of the fact that a few senior ministers of state were left out of the statement. Those who did not sign were Dr Lam Pin Min, Dr Maliki Osman and Mr Heng Chee How.

"They didn't intend to (leave them out), and I don't think you should put a lot of weight on that," he said.

PM Lee has reiterated that he intends to hand over the reins to his successor after the next election.

On what role this person will play in the next general election, which has to be called by April 2021, he said: "He will have to pull his weight and... show that he deserves to be what his peers and his colleagues in Cabinet think that he can do.

"This is necessary. If you are unable to win elections, you cannot be the leader. You can be a great thinker, you can be a great planner, but you have to be in politics."