The plan is a "one-off agreement. It will not be repeated," Prime Minister Malcolm Turnbull said at a press conference.
Turnbull added that the deal would only be available "to those currently in the regional processing centers" and will prioritize "women, children and families."
Around 1,300 people
are currently being held in offshore detention on the Pacific Island nation of Nauru, and Papua New Guinea's Manus Island.
Shirdel Eskandari Khah is one of them. He has a young son and has been on Nauru for two and a half years, and told CNN he is "really happy" about the deal.
The majority of the detainees
come from the Middle East and South Asia, with Iran and Afghanistan providing the bulk of the refugees.
Last month, Amnesty International accused the Australian government of turning Nauru into an "open-air prison
Numerous human rights abuses
have been documented at the centers.
In October, a UN committee report
found multiple cases of "attempted suicide, self-immolation, acts of self-harm and depression" among children who had lived in prolonged "detention-like conditions."
Support for the offshore detention system -- which has cost Australia upwards of $7.3 billion, according to Amnesty -- remains strong in Canberra. Turnbull recently introduced new legislation
that would prevent refugees and asylum seekers from ever settling in Australia if they came to the country by boat.
During the general election earlier this year, opposition leader Bill Shorten pledged a "more humane and safer approach to asylum seekers," but his Labor party remains committed to offshore detention.
Critics of the system operate under an "atmosphere of fear, censorship and retaliation
," a UN investigator warned last month.
'Not a plan'
Speaking Sunday, Turnbull did not set out a time frame for the deal, nor did he offer any information on how many refugees would be covered by it.
The deal will be administered by the UN High Commission on Refugees, Turnbull said, and "will take time."
In a statement
, the Human Rights Law Center criticized the government's announcement as being "full of holes."
"No time frame. No numbers. No detail on what the government will do with the hundreds of innocent people who will be left behind. It's not a plan," HRLC's director of legal advocacy Daniel Webb said.
"This ugly chapter in our history only closes when every single man, woman and child suffering at our government's hand on Nauru and Manus is finally rebuilding their lives in safety. No one can be left behind."
Oxfam Australia issued a statement calling on the government to "bring to Australia anyone not covered by the agreement with the United States."
The resettlement deal has been signed between the Turnbull and Obama administrations, and it is unclear how, if at all, it might be affected by Donald Trump's coming to power.
Speaking in New Zealand Sunday
, Secretary of State John Kerry said that the US had "agreed to consider referrals from UNHCR on refugees now residing in Nauru and in Papua New Guinea."
He did not respond to a question about whether the deal could be overturned by Trump.
Khah, the refugee on Nauru who CNN spoke with, said he thinks Trump is much better than Australian politicians.