Impeachment or early resignation - these are the two options facing South Korean President Park Geun Hye, whose entanglement in an influence-peddling scandal has seen her approval ratings plunging to new lows.

Either way, analysts say it is inevitable that the country will have to elect a new leader months ahead of the scheduled presidential election next December.

The three main opposition parties yesterday said they would propose an impeachment motion in Parliament, adding that a vote will be held next Friday.

But the ruling Saenuri party - whose support is necessary to push an impeachment through - is hoping Ms Park would step down next April and the presidential polls be held in June. It has given her until next Wednesday to decide.

Once Ms Park steps down, an election must be called within 60 days.

The plan will buy some time for Saenuri, which is still lacking a strong presidential candidate.

The party appears to be courting United Nations chief Ban Ki Moon, and talk has it that Ms Park is hanging on to her position to wait for him to finish his term on Dec 31.

Mr Ban, who has yet to officially declare his bid, is well respected for his international achievements and was a favourite candidate in early opinion polls. But it is uncertain if he will want to contest on the ticket of the troubled Saenuri.

Dr Katharine Moon, Korea expert at the Washington-based think- tank Brookings Institution, said Mr Ban has broad appeal. Having been a career diplomat, he "has no domestic base, and therefore, no domestic track record to praise or criticise".

But the opposition parties are not lacking in presidential hopefuls. The Democratic Party's Mr Moon Jae In and Mr Lee Jae Myung are leading in the latest survey by pollster Research View.

Mr Moon, a human rights lawyer who ran against Ms Park in 2012, is the most popular, with 23.8 per cent support, while Mr Lee, mayor of Seongnam city who has been compared to US President-elect Donald Trump for his brash ways, is second with 17.2 per cent.

Mr Ban is third with 15.2 per cent, ahead of Mr Ahn Cheol Soo (6.9 per cent), a businessman who founded the minor People's Party.

With Saenuri's approval rating plunging, analysts say the opposition will have a bigger chance of winning the next election.

But Dr Moon warned: "My serious concern is that people are looking at the short-term satisfaction of getting rid of Park rather than the more important question of what kind of mandate and policy agendas they expect to communicate to a new president."

Yonsei University political science professor Moon Chung In said South Koreans will want a leader who is different from Ms Park - someone humble who can communicate and empathise with them.

He added that Mr Moon seems to be the best fit so far, calling him a "very solid guy".

But Dr Lee Seong Hyon of local think-tank Sejong Institute pointed out that Mr Moon has yet to garner enough support from the conservative camp, and that people's dissatisfaction with Ms Park has not led to his increased popularity.

Seongnam mayor Mr Lee, given his rising popularity, appears to be the dark horse. Dr Lee said he stands out for being outspoken but his appeal is more liberal than broad, and he has yet to prove himself as good "presidential material".

Mr Ahn is seen by people as honest and good-hearted, but he lacks charisma as a leader, said Dr Lee.

"At a time like this, with great uncertainty, people are naturally inclined towards someone with charisma and strong leadership. People need a fire fighter who could hold their hands and guide them out of a burning house," said Dr Lee.

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