Home Affairs minister Peter Dutton says the roughly 90 asylum seekers held in offshore detention who have refused an offer under the United States settlement deal are waiting in case a future Labor government decides to open a pathway to settle in Australia.
Labor remains committed to offshore processing and boat turnbacks, with at the opposition's upcoming national conference.
Mr Dutton said the 90 who had refused the option to settle in the US so far were a "significant number".
"If you are a legitimate refugee I think like millions before you would be happy to go to the US," Mr Dutton said.
"They have pulled out of going to the US now because they believe that if a Labor government is elected they will be coming to Australia."
Several hundred refugees have now been settled in the United States under the Obama-era deal that was upheld by Donald Trump, despite his reluctance, as exposed in a leaked transcript of his phone conversation with Malcolm Turnbull in the early days of his presidency.
Labor leader Bill Shorten says the government has ignored New Zealand's offer to settle more people and hasn't tried hard enough to find other countries.
Mr Dutton cast doubt on Labor's plan to negotiate with new third countries to take asylum seekers stuck on Manus Island and Nauru, as the government is "constantly" trying to find new places to send them.
"There are no prospective cases," Mr Dutton told reporters in Canberra on Wednesday.
"You can go to Europe at the moment and if you can get a deal out of a European nation to take our people from Australia or wherever it might be, let me know about it.
"We have a people smuggling ambassador, we have a whole effort with Operation Sovereign Borders, within DFAT, within my department of Home Affairs.
"We're constantly, in detailed fashion, talking to third countries. The United States is it."
Mr Shorten said the United States deal was a good one, and Australia can have strong borders.
"(But) that doesn't mean you keep people in indefinite detention on Manus and Nauru because the government of the day is too lazy to negotiate resettlement arrangements with other countries," he told reporters.
"Just because the government has failed, doesn't mean we should accept their failure as our benchmark."
More than 400 asylum seekers have been resettled in the United States, but Mr Dutton says some are refusing to go because they believe they will settle in Australia under a potential Labor government.
Mr Shorten is promising to continue the government's policy of turning back asylum-seekers' boats where it is safe to do so, and continue offshore processing.
"Bill Shorten's quite cute with his words about third countries, all he says is 'oh we'll enter into discussions and negotiations' - no kidding," Mr Dutton said.
"We've done that for the last five years and it's not easy."
Labor's immigration spokesman Shayne Neumann said the New Zealand offer had been on the table since 2013 and the coalition had ignored it.
Labor is trying to amend national security laws to give doctors more power to order medical transfers off Nauru.
Mr Dutton said the current regime of medical transfers was working. He confirmed 810 people had been brought to Australia from Nauru for medical treatment, and only a small number had gone back to the island nation.
