Published: 2017-03-21 01:01:14 BdST
New Zealand police said they responded to the incident near the capital Wellington on March 12 involving an employee of the US Embassy.
They did not say what work the employee did or give any other details.
The US government later declined a police request to waive the employee's diplomatic immunity, the New Zealand Foreign Ministry said on Monday.
The New Zealand Herald at the weekend identified the man as an embassy attaché and said he had left country with a broken nose and black eye.
A spokeswoman for the US Embassy said it was in touch with New Zealand authorities.
"We take seriously any suggestion that our staff have fallen short of the high standards of conduct expected of US government personnel," the spokeswoman said.