Australia has accepted, "in principle", a longstanding offer from New Zealand to resettle up to 150 people per year who had been kept in the Australian government's offshore detention centres. 

The deal means asylum seekers, some who have been held indefinitely in limbo in such centres on Manus Island and Nauru, could soon come to New Zealand. 

The deal was confirmed "in principle" in the Australian Senate this week but awaits further negotiation, including Australia seeking a guarantee there would be no "backdoor" for the people transferred to come to Australia. 

Australia's Home Affairs secretary Mike Pezzullo said the two countries had been in extensive negotiations at ministerial level and the matter was currently before the New Zealand Cabinet for its final approval. 

After that response was received the Australian government would then have to consider the conditions, he said. 

Pezzullo said they were seeking an "early resolution" but was reluctant to even say it would be resolved "this year". 

"Because I think we've said that before, and that was last year," he said. 

He said it had been agreed to in principle but "subject to the satisfaction of both parties and the resolution of a number of issue". 

Pezzullo said Australia wanted a guarantee there would be no "backdoor" for the people transferred to come back and settle in Australia. 

Immigration Minister Kris Faafoi has been approached for comment. 

Asked about this issue last year Faafoi said New Zealand intended anybody resettled here would have the "full rights of New Zealand citizens", which included the right to travel to and work in Australia. 

"Any intention Australia has in that is their decision," Faafoi said. 

"We have made it pretty clear on a number of occasions, if they come here, they will eventually become New Zealand citizens, and we would like them to have the full rights of New Zealand citizens." 

Refugee activists, meanwhile, have welcomed the news. 

"This is a very long and hard-earned human rights win," said Meg de Ronde, executive director of Amnesty International Aotearoa New Zealand. 

"We're relieved that for hundreds of people, the torture is nearly over and soon they will get to begin rebuilding their lives."