The United States and Australia have agreed to a one-off refugee resettlement deal for people on Manus Island and Nauru.

Key points: Resettlement deal is a "one-off" that will only apply to refugees currently on Manus Island or Nauru, Malcolm Turnbull says

Resettlement deal is a "one-off" that will only apply to refugees currently on Manus Island or Nauru, Malcolm Turnbull says US Homeland Security officials coming to Australia to begin process in next few days

US Homeland Security officials coming to Australia to begin process in next few days Peter Dutton says Government in final stages of negotiation with Nauru for 20-year visa

Prime Minister Malcolm Turnbull confirmed the agreement this morning, following a year of negotiations.

Speaking in Canberra alongside Immigration Minister Peter Dutton, Mr Turnbull said the deal would only apply to those currently on Nauru and Manus Island and not to any new asylum seeker boat arrivals.

"It is a one-off agreement — it will not be repeated," he said.

Authorities hope to begin moving people to the United States by early next year.

Mr Turnbull would not be drawn on the number of refugees that would be resettled as part of the arrangement, but he said the priority was "very much on the most vulnerable" — in particular, families on Nauru.

The final figure will be up to American officials from the Department of Homeland Security, who will arrive in Australia to begin the vetting process in the next few days.

The ABC understands the offer will be made to the vast majority of people still in offshore detention centres, as well as those processed offshore but currently in Australia due to medical reasons.

The offer will not be made to those who have accepted resettlement elsewhere.

Those who do not accept the resettlement deal with the US are set to be sent to Nauru and provided a 20-year visa to stay on the island or return to their country of origin.

'Ring of steel' around Northern Australia

A "significant" Defence operation is now underway in waters off Northern Australia, with the Federal Government anticipating an increase in attempted boat arrivals by people smugglers.

"We recognise that people smugglers will seek to exploit this announcement," Mr Turnbull said, repeating the Coalition's policy of intercepting boats and turning them back to Indonesia or the Indian subcontinent.

Sorry, this video has expired Dutton says future arrivals won't be resettled to the US

The precise number of Defence assets is not known, but government sources describe the operation as a "ring of steel", and one of the largest ever peace-time deployments.

Immigration Minister Peter Dutton said the Federal Government would still be reliant on Nauru as part of the Federal Government's border protection policies.

"We still rely on regional processing, which is why Nauru will remain in its current status forever," he said.

"Let that be a very clear message to all people that you will not step foot on Australian soil."

Opposition Leader Bill Shorten said Labor had not been briefed on the agreement, but welcomed the announcement.

"Labor would be hypocritical if we didn't welcome this because this is the very thing we wanted with the Malaysia solution," he said.

Mr Dutton said people who "aren't owed protection need to return back to their country of origin".

"It is important to point out 650 people have already done that," he said.

Mr Dutton also referred to the proposed changes to the Migration Act, urging the Senate to pass the bill which would ban people on Manus Island and Nauru from ever coming to Australia.

It is understood the proposed resettlement deal is not strictly contingent on the bill being passed through Parliament.

US 'proud' of plan to help refugees in Nauru, PNG

Afghan refugee Riaz Samadi in Port Moresby said he felt "very happy" about the "very good deal".

"The Australian Government did a good deal with the US. I felt very good when I heard this news in the morning," he said.

"I feel it was very good and I am very happy, and I just think about the future.

"Whatever happened to us in the past, I just try and forget that and think about the future."

Kurdish-Iranian refugee Behrooz Bouchani, who is in detention on Manus Island, said reactions among refugees had been mixed.

"People in Manus detention are really happy that eventually they got good result and they will go to a safe country," he said.

"But some people are so sad because they are worried about their future.

"The Government has kept them here for near four years, and I think it's enough that we can say that they are real refugees and I think that the Government has to offer them American option too."

Malcolm Turnbull would not be drawn on the number of refugees that would be resettled. ( ABC News: Luke Stephenson )

James Carouso, charge d'affaires for the United States Embassy in Canberra said the US was committed to protecting refugees.

"We have a strong commitment to protecting vulnerable refugees around the world, and are proud to be part of a plan to help some of the vulnerable refugees in Nauru and Papua New Guinea who are in need of resettlement," Mr Carouso said in a statement.

"The United States has robust cooperation with the Government of Australia on a wide variety of issues, including on refugees, and we commend their long-term commitment to formal refugee resettlement and providing humanitarian assistance worldwide."

The ABC understands the Federal Government has been talking with the United States, Canada, Malaysia and New Zealand about resettling refugees from Manus Island and Nauru.

Refugee groups welcome deal but want more detail

Refugee advocates have welcomed the resettlement deal, but say an agreement should have been sought earlier following ongoing concerns about the welfare of those on Manus Island and Nauru.

Questions have also been raised about whether the incoming President-elect Donald Trump will honour the deal.

Human rights lawyer David Manne said the Federal Government could have handled the issue better.

"It would have been better if Australia shouldered its responsibility to these people and resettled them in Australia, but the fact is if there is a potential option that does deliver them safely that must be welcomed.

Daniel Webb, from the Human Rights Law Centre, said while the deal was welcome, there was not enough detail.

"What we've heard this morning is full of holes. No timeframes, no numbers," Mr Webb said.

Lawyer representing refugees Ben Lomai said the issue of compensation still remained.

"The only issue that is left remaining to be at rest now is the issue of compensation — how much and how should be paid to individual asylum seekers," he said.

In a statement, the United Nations Refugee Agency (UNHCR) welcomed the agreement but said it was not party to it.

The organisation added that it remained "gravely concerned" about the fate of all vulnerable individuals in Papua New Guinea and Nauru.

"Appropriate solutions must be found for all of them," it said.