Sydney (AFP) - Millions of Australians are "sickened" by the imminent execution of two of its citizens by Indonesia, Prime Minister Tony Abbott said on Sunday, warning of a tough diplomatic response.

His comments came as the families of Andrew Chan and Myuran Sukumaran made emotional last-gasp pleas to Indonesian President Joko Widodo.

"I beg him (Widodo) again and again to please forgive them and give them, both of them, a second chance," Sukumaran's tearful grandmother Edith Visvanathan told reporters.

A statement from the Chan family said Andrew Chan "continues to pray".

"While there is life, there is hope. Let them live," it said.

No date has been set for their killing, but Indonesia has said governments with citizens on death row have been invited to talks at the foreign ministry on Monday.

Chan, 31, and Sukumaran, 33, are facing execution by firing squad as early as this week as ring leaders of the so-called Bali Nine group trafficking heroin from Indonesia's island of Bali into Australia.

While all hope appears to be lost, Abbott put pressure on Jakarta for the second day in a row.

"Millions of Australians are feeling sickened by what might be about to happen in Indonesia," he told Channel Ten.

"If these executions go ahead, and I hope they don't, we will certainly be finding ways to make out displeasure felt."

Brazil and The Netherlands recalled their ambassadors in protest at executions of their citizens in January. Abbott has not said what Canberra's response would be.

Foreign Minister Julie Bishop last week warned Jakarta that Australians could boycott Indonesia, including the island of Bali, a popular holiday spot for its travellers.

Abbott also stepped up criticism of Indonesia for trying to save its own citizens on death row in other countries for drug trafficking while rejecting pleas from Australia.

"What we are asking of Indonesia is what Indonesia asks of other countries when its citizens are on death row," he said.

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"If it's right for Indonesia to ask and expect some kind of clemency, it's surely right for us to ask and expect some kind of clemency."

There are 360 Indonesians on death row around the world, including in Malaysia, Singapore, China and Saudi Arabia, Australian media reported. Of that, 230 are on drug charges.

As time runs out for Chan and Sukumaran, attorneys-general from across each of Australia's states and territory have sent a joint letter to Indonesia's government asking they be spared, broadcaster ABC reported.

Their families were presented Sunday with a petition signed by more than 150,000 people urging clemency.

Chan and Sukumaran, who have been on death row since 2006, claim they have been rehabilitated but lost their appeals to Widodo, who has vowed a tough approach to ending what he has called Indonesia's "drug emergency".

Widodo has been a vocal supporter of capital punishment and recently executed six convicted drug smugglers.