The move comes the day after prosecutors named Park a criminal suspect in a major influence-peddling case, tightening the noose on an already hugely unpopular leader.
"We will immediately review the timing and methods of impeachment and set up a subcommittee to review a push for impeachment," said Choo Mi-Ae, head of the opposition liberal Democratic Party.
Two smaller opposition parties have already said they will seek to remove her.
Lawmakers have been under growing public pressure to oust Park, with weekly mass protests drawing hundreds of thousands of protestors across the country.
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On Sunday, Seoul prosecutors said Park had colluded with her long-time friend, Choi Soon-Sil, who is accused of coercing more than USD 60 million from local firms and meddling in state affairs.
Park's single, five-year term ends in February 2018, and observers say she is likely to do all she can to serve out her time because a sitting president cannot be charged with a criminal offence except insurrection or treason.
The three opposition parties hold a combined 55 per cent of parliamentary seats -- short of the two thirds majority required to pass an impeachment bill.