A US Marine in the NT has tested positive for COVID-19 while in quarantine.

The 19-year-old man arrived in Darwin on May 9 and tested positive in the past 24 hours.

The patient is asymptomatic and is under the care of NT Health at the NT Centre for National Resilience.

The total number of cases diagnosed in the Northern Territory is 172.

All cases have been related to international or interstate travel, with no cases of community transmission.