The group, Human Rights Watch, says the Papua New Guinea government should present its plan and timeline for closing the Manus Island detention centre at the upcoming review of its human rights record.
On Friday, the United Nations Human Rights Council in Geneva is due to examine PNG in its Universal Periodic Review.
Human Rights Watch says countries should ask PNG officials to elaborate on immediate plans to implement the PNG Supreme Court decision which declared the detention of Australia's asylum seekers and refugees on Manus illegal.
Nine days after the ruling, talks are still being held between PNG and Australia over the court ruling amid apparent disagreements over who is responsible for the more than 800 people detained illegally.
PNG has said it will close the detention centre while Australia says it won't take back any of the people it had moved to Manus.