Immigration Minister Peter Dutton has suggested politics played a role in the blocking of his bid to deport six refugees, after some had travelled to Iran to go "back for a holiday".

One man, who had told the Federal Government he was at risk of execution in Iran, made three return trips to the country, while another travelled back to get married.

Mr Dutton wanted the men deported, along with four others.

But the Administrative Appeals Tribunal (AAT), which reviews decisions made by Federal Government ministers, departments and agencies, blocked the bid.

Mr Dutton said it was important to note the tribunal's president Justice Duncan Kerr, whose term expired on Monday, was a former federal Labor MP.

"When you look at some of the judgements that are made, the sentences that are handed down it's always interesting to go back to have a look at the appointment of the particular Labor Government of the day," Mr Dutton told Sydney radio station 2GB.

"Anyway, it's a frustration we live with."

Justice Kerr will remain as a Federal Court judge and Mr Dutton said the Government will make "new appointments" when they come up.

"We won't continue the appointments of some people and that's how the system works," he said.

Attorney-General George Brandis on Monday thanked Justice Kerr for his "outstanding service to the Commonwealth".

"Justice Kerr has provided strong leadership to the AAT and will be remembered as a very successful president," Senator Brandis said in a statement.

Mr Dutton told Melbourne radio station 3AW it was frustrating when decisions made by him and Immigration Department officials are overturned by the AAT.

"Some of these cases are infuriating and without commenting on the six here there are many cases that I look at where, on the facts available to me, you shake your head," he said.

Dutton unsure when US will take refugees

In a later interview, Mr Dutton said he did not know when the United States would begin taking refugees from Manus Island and Nauru.

The deal to take refugees was brokered between the Federal Government and the US in the closing weeks of the Obama administration.

US officials have been working to assess people on both islands under the agreement, and Mr Dutton told Sky News while the US was under no obligation to take a certain number of people, the process was going smoothly.

"We'll see how we go over the next little while, but they are putting no roadblocks in the way," he said.

"They are working conscientiously in the spirit of the deal, and I'm keen to get people off Manus."

Mr Dutton said Australia and Papua New Guinea wanted the Manus centre shut before November, despite asylum seekers reacting angrily when told to leave to it can be demolished.

"Now, as they can see, the Government is definite about the closure date and will work towards that 31 October date with the PNG authorities and with our own people to make sure that's a reality," he said.