Refugees on Manus Island and Nauru are set to learn whether they will be accepted for resettlement to the US.
US authorities started sending appointment slips to refugees on Tuesday afternoon.
Refugee Action Coalition spokesman Ian Rintoul told AAP he was aware of 25 people on Nauru receiving appointment times for Wednesday so far.
"People are a bit surprised, some people had given up hope that it would happen," he said.
"Right now they're experiencing anxiety and anticipation."
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A spokeswoman for Immigration Minister Peter Dutton declined to comment saying he would not be making a running media commentary about the US processes.
The agreement, struck with the Obama administration, involved the US accepting up to 1250 refugees in limbo in Papua New Guinea and Nauru, in return for Australia taking asylum seekers from Central America.
More than 1600 refugees have expressed interest in the US resettlement deal.
The agreement was the subject of a heated phone call between Donald Trump and Prime Minister Malcolm Turnbull in January where the new US president characterised the deal as dumb.
Mr Trump has since reluctantly agreed to honour it.
The Manus Island detention centre is slated for closure by the end of October.
