The United States is only option for resettling asylum seekers and Labor will struggle to find somewhere else to take them, Home Affairs Minister Peter Dutton says.
But Labor leader Bill Shorten says the government has ignored New Zealand's offer to take 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 allow for faster medical transfers off Nauru, but Mr Dutton says it will mean the end for offshore processing.
He also 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.
Australian Associated Press