Mr Key was uncertain about when Muhammed Rizalman bin Ismail would be sent back from his home country, where he returned with diplomatic immunity in May after being charged with attacking a Wellington woman in her home.
Malaysia's Prime Minister Najib Razak told Mr Key in July that Rizalman would be returned to face the charges of burglary and assault with intent to rape.
It was initially believed he would return immediately, but the case has dragged out over several months.
Mr Key told reporters at his post-cabinet press conference today: "It's still before the courts and I don't really have much of an update, except to say that we're confident the process will its course and the gentleman will return to New Zealand.
"We're just working our way through a long legal process."
Asked whether he was comfortable with the length of time it was taking for Rizalman to be sent to New Zealand, Mr Key said: "We would prefer it was quicker but in the end I take a lot of store out of the personal assurance that Prime Minister Najib gave me.
"There's no reason for the Malaysians to make it any more difficult than it should be. He'll have his own legal rights but I'm confident he will return to New Zealand."
Mr Key said he could not give a time frame for Rizalman's return.
The former adviser at the Malaysian Embassy was arrested on May 10 after allegedly following Tania Billingsley to her Brooklyn home and attacking her.
The Ministry of Foreign Affairs and Trade (Mfat) asked Malaysia to waive immunity so he could face the charges, but behind-the-scenes communication led Malaysia to believe he could return home.
An independent inquiry is looking at how Rizalman was allowed to leave New Zealand. Mfat says the inquiry is ongoing.
- Isaac Davison of the New Zealand Herald
