Gabe Watson was released from prison last week after serving an 18-month sentence for the manslaughter of his wife, Tina, in 2003 during a trip on Australia's Great Barrier Reef. He was being held in immigration custody until Australia - a staunch opponent of the death penalty - received assurances that he would not face capital charges in his home state of Alabama.
Prosecutors in Alabama, a pro-death penalty state, want to try Watson again over his wife's death, and are expected to seek murder charges.
An immigration spokeswoman, speaking on condition of anonymity because of department policy, said the Australian government had received assurances from US officials that "the death penalty would not be sought, imposed or carried out."
"We are now satisfied that our international obligations have been met and are commencing plans for Mr. Watson's removal," she said.
She would not give details on the timing of his deportation but said it would be "as soon as possible".
Adrian Braithwaite, Watson's Brisbane-based lawyer, said the Australian government had refused to show him a copy of the US assurance because it was a diplomatic document, but he had renewed his request to see it.
"At the moment I'm not taking the word of the government that they have received the assurances," Braithwaite told The Associated Press by telephone. "I want to be provided with a copy of the correspondence received from the United States so that we can be satisfied it's a binding assurance and properly advise our client."
He said the immigration department had pledged to provide him with 48 hours notice before Watson was put on a plane.
He said Watson was ready for whatever may happen upon his return to the United States."He's not running scared from what might occur in Alabama," Braithwaite said.
Watson was dubbed the "Honeymoon Killer" by the Australian media after his wife of 11 days, 26-year-old Tina Watson, drowned during a 2003 scuba diving trip.