New Zealand is seeking a Malaysian diplomat charged with sexually assaulting a 21-year-old woman in Wellington last month.
Muhammad Rizalman bin Ismail, 38, has since returned to Malaysia with his family, claiming diplomatic immunity.
Malaysia's Foreign Minister Anifah Aman told reporters that the accused would be sent to New Zealand "if it is absolutely necessary".
He added that a defence ministry panel would investigate the matter.
Prime Minister John Key told reporters that New Zealand preferred that diplomatic immunity was waived so that the diplomat could face trial in New Zealand and, if not, called for him to be prosecuted in Malaysia.
In remarks reported by the New Zealand Herald newspaper, he said: "We made it quite clear that we were under no illusion about how seriously New Zealand took the issue, and we expect the person to be held to account."
The diplomat had been working at Malaysian High Commission in Wellington as the staff assistant for defence for the past year.
He has been charged by Wellington police with burglary and assault with intent to rape. Each charge carries a maximum prison sentence of 10 years.
He is accused of following a 21-year-old woman to her home in the suburb of Brooklyn on 9 May and attacking her there.
New Zealand and Malaysia have conflicting accounts on how the diplomat left for home.
New Zealand released documents on Tuesday to local media showing that the Malaysian High Commission refused to waive diplomatic immunity for the accused, reported news website Stuff.
However Anifah Aman, the Malaysian foreign minister, told a press conference that initially Malaysia was willing to waive diplomatic immunity, but during discussions New Zealand had offered "an alternative" for the accused to be brought to Malaysia.
He added that the defence ministry had established a board of inquiry to investigate the case thoroughly, and had given an assurance that "it will not compromise or conceal any facts on the case".
Asked whether extradition was a possibility, he said he would consider it if New Zealand felt the Malaysian investigation was not being conducted properly and requested it.
He also told local newspaper The Star that the government was not protecting the diplomat.
"Just because he is a diplomat does not mean he gets off scot-free. Diplomatic immunity is not about having the licence to commit crime," he was quoted as saying.