Australia's prime minister says he still holds out hope that Indonesia will not execute two Australian drug traffickers on death row, saying mercy must play a part in the Indonesian justice system.

Myuran Sukumaran and Andrew Chan were sentenced to death in 2006 for their leading roles in a plot to smuggle heroin from the Indonesian resort island of Bali to Australia.

Prime Minister Tony Abbott told Sydney Radio WSFM on Tuesday he had made strong representations on the Australians' behalf to the Indonesian president.

He declined to say if Australia could withdraw its ambassador to Indonesia in protest if the Australians are executed, as the Dutch and Brazilian governments have done in protest over their own nationals being killed by firing squad.