Karl Rove, who was an advisor and deputy chief of staff to George W. Bush, made the comments to Peta Credlin and Kristina Keneally on Sky News on Wednesday night.

Mr Rove said if all those kept on Manus Island and Nauru were on US soil by January 20, there may be "little ability to undo the deal".

However, if the asylum seekers remained in transit, Mr Rove said the deal could easily be stopped by president-elect Donald Trump.

"If you don't get it done, that is to say if these people are not transferred off of your offshore centres into the United States by the 20th of January, he can easily stop it," Mr Rove said.

"This is an informal agreement between our two countries, not a treaty. It doesn't require senate confirmation, [it] doesn't require approval by anybody except the signature of the president or the signature of the secretary of state.

"So those 1800 people, you better get them on airplanes - fill a lot of Qantas planes flying to the United States if you want to keep this problem off of your agenda and in the United States.

"Get them here by the 20th of January, otherwise my suspicion is the new administration would not feel bound by the agreement that John Kerry has made with the Turnbull government."

On Sunday, the same day the deal was announced, Mr Turnbull said he was "confident" it would not be wound back by Mr Trump.

"The United States government meets its commitments from one administration to another," he said.

However, he remarked that he would like the transfer to be processed quickly.

"[US] officials will be coming to Australia in the next few days and then travelling up to Nauru," he said on Sunday.

"Obviously, we'd like to see this arrangement proceed in a speedy manner, but that is very much in the hands of the United States government."

Ms Credlin, the former chief of staff to Tony Abbott during his Prime Ministership, said Mr Rove's comments were "very telling".

"There's a lot of movements that now need to happen out of Nauru and Manus Island," she said. "We're talking about two months here ... there's a lot of logistics that have got to go right."

She said getting the asylum seekers processed in time would "depend on security clearances".

"It will really depend on how much ASIO and others have done in background checks, how much the UN agencies have done, and how much the Americans will want to do their own checking," she said.

Under Australia's deal with the United States, 1800 detainees on Manus Island and Nauru will be encouraged to return home, seek resettlement in the US, or be issued a 20-year visa for Nauru.