South Korea is negotiating conditions with New Zealand Police which may result in a senior diplomat accused of sexual assault extradited here to face trial.

Hongkon Kim has been charged with three counts of sexual assault involving a male staff member at the South Korean Embassy in Wellington in 2017.

Facing pressure from New Zealand, South Korea ordered Kim back to Seoul this week and dismissed him from his position as consul general in the Philippines.

The Foreign Ministry in Seoul has been quoted in Korean media as saying: "If the New Zealand Government request our co-operation in seeking criminal justice, the Ministry of Foreign Affairs will co-operate."

It said that it does not tolerate sexual crimes but has yet to decide how to handle the case.

A contact close to South Korean authorities told the Herald New Zealand's Ministry of Foreign Affairs and Trade have been told of Seoul's willingness to co-operate in the matter now, and negotiations are ongoing for terms on Kim's extradition.

But when approached, an MFAT spokeswoman said is was making no further comment on the matter and said questions on extradition would need to be directed to the New Zealand Police.

MFAT had sought a waiver of diplomatic immunity from Seoul to allow police to conduct inquiries at the South Korean Embassy last September, but this was declined at the time.

Kim left New Zealand in February 2018, and an MFAT spokeswoman said he no longer had diplomatic immunity as he was no longer in New Zealand.

A police woman said police were not in a position to provide "further specific details" at this time because the matter was still ongoing.

A spokesman for Prime Minister Jacinda Ardern confirmed she had spoken to South Korean President Moon Jae-In last Tuesday, and had asked Moon to send the suspect back to Wellington to face charges.

The Herald understands the u-turn by Seoul was because it needs New Zealand's support for its bid to install its candidate, Trade Minister Yoo Myung-hee, as director general of the World Trade Organisation.

Having New Zealand's backing is seen as crucial because NZ Ambassador David Walker, a permanent representative to the WTO, chairs the general council which is the organisation's top decision-making body.