An American man convicted of manslaughter in his wife's honeymoon death was deported Thursday from Australia to the United States, where he is likely to face murder charges for the 2003 drowning.

Gabe Watson, 33, boarded a flight from Melbourne accompanied by Immigration Department staff and Queensland state police officers, Immigration Minister Chris Bowen said.

Watson had been in immigration custody since completing an 18-month prison sentence earlier this month. Australia, a stanch opponent of capital punishment, delayed his deportation until it received a pledge from the U.S. government that it would not seek the death penalty against Watson.

Prosecutors in Alabama, Watson's home and a pro-death penalty state, want to try him again over his wife's death, and are expected to seek murder charges.

Bowen said Watson returned voluntarily after both Alabama and U.S. federal authorities guaranteed that he would not face the death penalty.

"The Australian government received assurances from the United States government that should Gabe Watson be returned to the U.S., the death penalty would not be sought, imposed or carried out in relation to this crime," Bowen said.

Under Australia's Extradition Act, a person cannot be deported to face prosecution on a capital charge unless there is an assurance the death penalty will not be imposed.

Watson's lawyer, Adrian Braithwaite, said his client was happy to go.

"He's looking forward to returning home and successfully defending himself if there's a trial there," Braithwaite told The Associated Press.

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 on the Great Barrier Reef with her husband, an accomplished diver.

In 2008, the Queensland state coroner found there was sufficient evidence to charge Watson with her death, and he was officially charged with murder a few months later.

In 2009, Watson — who had remarried — traveled to Australia to face trial.

Officials in Queensland state argued he killed his wife by turning off her air supply and holding her underwater. When Watson pleaded guilty to the lesser manslaughter charge last year, he was sentenced to 18 months — a punishment Tina Watson's family and Alabama authorities slammed as far too lenient.

Queensland Coroner David Glasgow said a possible motive for the killing was Tina Watson's modest life insurance policy.

Alabama Attorney General Troy King has said he believes Watson devised a plot in Alabama to kill his wife on their honeymoon, which would give the U.S. state jurisdiction to charge him. King has argued there are no international standards on double jeopardy that prevent Alabama from trying Watson again over the death.

Bowen said it was not an issue for Australia whether there was a new prosecution.

"My role has been to ensure that we fulfill our treaty obligations, we've done that," Bowen told reporters in Canberra. "Double jeopardy is not covered by our treaty obligations."

"There is various speculation about what Mr. Watson may or may not be charged with — I've seen some speculation that they would be different charges to what he's been charged with in Australia — but that is not a matter the Australian government has a role in," he said.

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Associated Press writer Tanalee Smith contributed to this report from Adelaide.