The wife of an Australian heroin trafficker who has had his death penalty in Vietnam commuted to life in prison says she is relieved but sad that he may never see their children again.

The Vietnamese President yesterday commuted Tran Van Thanh's death sentence for trafficking heroin from Vietnam to Australia as part of a seven-member gang commuted to life imprisonment.

His wife, Do Lan Tran, who lives in Cabramatta with the couple's two young sons, said her sister-in-law had visited him in prison in Ho Chi Minh City on August 5.

"My sister-in-law saw him … just three days before Kenny [one of his sons] turned six and all he wanted was to see him and kiss him," she said.

"Now he cannot come home ever. Of course, it is better than the shooting … one day I can only hope the governments will agree to let him serve his time in an Australian jail."

Mrs Tran said Australian authorities had done all they could to help her husband.

The Foreign Affairs Minister, Alexander Downer, said Vietnam's President, Tran Duc Luong, had reduced Tran's sentence on humanitarian grounds and because of the good relationship between the two countries.

The Prime Minister, John Howard, and Mr Downer had urged the President not to impose the death penalty.

A spokeswoman for the Department of Foreign Affairs said the commutation left three Australians sentenced to death by overseas courts.

Cong Thanh Mai and Nguyen Van Chinh are facing the death penalty in Vietnam, while Tuong Van Nguyen has been sentenced to death in Singapore.

Mr Downer has written to his counterpart in Vietnam seeking clemency for one and said yesterday that he would soon be writing to argue for a relaxed sentence for the other.