But the government has not said whether all of the detainees held in Australia's offshore detention centres would actually be resettled under the proposal.
Mr Turnbull said it was a one-off agreement reached after months of negotiations with the US and would not be repeated.
"It is only available to those currently in the regional processing centres. It will not be available to any persons who seek to reach Australia in the future," he told reporters in Canberra on Sunday.
here are currently just over 1000 detainees held in processing centres on Manus Island and Nauru.
The US Department of Homeland Security will be sending officials to start processing the detainees soon, according to the Prime Minister.
But when asked whether the deal guaranteed resettlement in the US, Prime Minister Turnbull gave no clear indication.
"We are not providing any more detail about the arrangements than we have today," he told the media.
The United Nations endorsed the proposal but asked for more detail.
"The full details of the agreement are not yet known, and UNHCR is not a party to it," the UN's High Commissioner for Refugees said in a statement.
"UNHCR's endorsement of these referrals under the humanitarian imperative does not alter Australia's obligations under international law, including the right to seek asylum irrespective of the mode of arrival."
