The Government of Tokelau says the three atolls are not yet in a position to effectively quarantine, isolate and manage a suspected or confirmed case of Covid-19.
The government had undertaken an assessment of preparedness levels.
It first shut its borders to visitors on 21 March.
The government said the safety of the people was of paramount importance, so the border restrictions would remain in place.
It said over the next three months it would focus on putting in place the infrastructure to allow the atolls to handle cases of Covid-19 among arrivals.