Australia is struggling to convince refugees held in offshore detention to voluntarily resettle in Cambodia under a bi-lateral deal, a refugee advocate group said on Friday, despite the government insisting that the first transfers are imminent.

Australia has been criticized at home and abroad for its tough immigration policies, including sending asylum seekers to camps in impoverished Papua New Guinea and Nauru, where they face long periods of detention.

In September Cambodia agreed to resettle potentially hundreds of refugees held at the Australian detention centre in tiny Nauru in exchange for an extra A$40 million ($31.16 million) in aid.