Prime Minister Tony Abbott has appealed directly to Indonesian president Joko Widodo to show mercy to two Australian men on death row in his country.

Myuran Sukamaran and Andrew Chan were sentenced to death in 2006 for their roles in the so-called Bali Nine’s attempt to traffic heroin to Australia.

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Sukumaran is not among the first group of six prisoners due to face the firing squad this Sunday, but on Thursday he was named as one of 16 prisoners, from a total of 64 on death row, who had been denied their pleas for clemency by the Indonesian president.

Chan’s chances of a reprieve appear equally doomed after president Widodo also made clear there was no prospect he would show mercy for any of the other prisoners on drug convictions.

A spokeswoman for the Prime Minister said the Government would continue to make representations to seek to avoid the execution of the two Australians.

Mr Abbott’s appeals came as the pair’s lawyer Julian McMahon said that stalling a final decision on the fate of the two men could be the one hope of saving them from the firing squad.

Mr McMahon conceded the bid to save the two prisoners’ lives would be an “uphill battle”.

He said if Chan’s clemency application could be deferred – perhaps indefinitely – Sukumaran may also be spared because of the requirement under Indonesian law that prisoners who commit a crime together must be executed together.

Mr McMahon said if the Abbott Government could buy time more for the two Australians, it may also help persuade the Indonesian president that Chan and Sukumaran have genuinely changed during their time in prison and have also had a “remarkably positive influence” on fellow prisoners.

“I have real confidence that the more [president Widodo] learns about their rehabilitation the more he will be prepared to have another look at this situation.”