Senate crossbencher Jacqui Lambie has offered to help the Morrison government unwind the laws, on one condition.

Senator Lambie has refused to publicly state what that condition is, citing national security concerns.

She said she was in constructive talks with Prime Minister Scott Morrison and Home Affairs Minister Peter Dutton.

"I can't feed out to any media what the condition is. Right now the talks are going along really, really nicely," she told AAP on Thursday.

"There's a game of trust there between myself, the PM and minister Dutton and I will not put that at risk."

But sources close to the negotiations told Nine newspapers her vote could be secured in return for accepting the New Zealand deal.

New Zealand has long offered to take 150 refugees per year from Australia's offshore processing centres in Papua New Guinea and Nauru.

The coalition and previous Labor governments have refused to accept the offer, claiming it could trigger an influx of asylum-seeker boats.

The bill is listed to be brought on for debate on Monday.

Refugee Behrouz Boochani, who spent more than six years in detention in Papua New Guinea, urged the government to seize the deal.

"Right now the government doesn't have any (other) way. They should accept New Zealand's offer," he told AAP.

"If they accept New Zealand's offer we can say that it's almost finished. It is a big chance for the government, a big opportunity."

Home Affairs Minister Peter Dutton is tight-lipped on the ultimatum.

"Obviously we've been in discussions with Jacqui and it's just not something I can comment on publicly at the moment," Mr Dutton told 2GB radio.

He needs Senator Lambie's vote to repeal the medevac laws.

"I think Jacqui can support the bill and she should support the bill, because it's very clear that we've brought people to our country who are of bad character," Mr Dutton said.

"There are six people who are here that we worried about and 10 on the way that we have, under the law, no ability to stop.

"They are people of poor character that we don't want in our country."

The medevac laws, which passed against the government's will earlier this year, gave doctors a greater say in granting medical transfers to sick refugees being held offshore.

There have been 179 people brought to the Australian mainland for treatment under the medevac laws.

Almost 500 refugees and asylum seekers remain on Nauru and in Papua New Guinea.

The Senate is expected to debate the medevac laws next week, before parliament breaks over summer.

Australian Associated Press