Tony Abbott has called on Indonesia to “reciprocate for Australia’s $1bn aid package after the 2004 tsunami by sparing two citizens on death row for drug smuggling.

The prime minister strengthened his public calls for clemency for Andrew Chan and Myuran Sukumaran with a warning on Wednesday that Australia would “feel grievously let down and would “make our displeasure known if Indonesia proceeded with the executions.

“Let’s not forget that a few years ago when Indonesia was struck by the Indian Ocean tsunami Australia sent a billion dollars worth of assistance, we sent a significant contingent of our armed forces to help in Indonesia with humanitarian relief and Australians lost their lives in that campaign to help Indonesia.

“I would say to the Indonesian people and the Indonesian government: we in Australia are always there to help you and we hope that you might reciprocate in this way at this time.

Indonesia’s foreign ministry spokesman Arrmanatha Nasir told reporters in Jakarta he had not studied Abbott’s comments on tsunami aid but understood he had made a linkage to “the issue now in Indonesia.

“I hope this does not reflect, the statements made, the true colours of Australians, Nasir said on Wednesday. “Threats are not part of diplomatic language and from what I know, no one responds well to threats.

Indonesian authorities announced on Tuesday that they were delaying the planned transfer of the pair to Nusa Kambangan and the executions were unlikely to occur this month.

Indonesia’s foreign minister, Retno Marsudi, said the government understood Australia’s position but “it should be underlined that this issue is purely a law enforcement issue, law enforcement against an extraordinary crime.

Abbott said the delay was “an encouraging sign and he hoped Indonesia “realised that its own best values and its own best interests are served by not going ahead with these executions.

Asked about the potential consequences of the executions, Abbott said: “We will be letting Indonesia know in absolutely unambiguous terms that we feel grievously let down.

He said he did not want to “prejudice the best possible relations with a very important friend and neighbour but I’ve got to say that we can’t just ignore this kind of thing if the perfectly reasonable representations we are making to Indonesia are ignored by them.

“We are doing no more for our citizens than Indonesia routinely does for its own citizens and if it’s right and proper for Indonesia to make these representations, if it’s right and proper for other countries to heed Indonesia’s representations, it’s right and proper for us to make the representations and for them to be heeded, he said.

Abbott said Chan and Sukumaran – who were part of the Bali Nine group that sought to smuggle heroin from Indonesia to Australia – deserved a long time in jail but they did not deserve to die.

“In fact, they have become, it seems, thoroughly reformed characters in prison in Bali and they are now helping the Indonesian fight against drug crime, so much better to use these people for good than to kill them, Abbott said.

Marsudi said on Tuesday the application of the death penalty was part of the law of Indonesia and “implemented as a last resort for the most serious of crimes and “not directed to a particular country.

The Australian foreign affairs minister, Julie Bishop, welcomed the decision to delay the transfers of Chan and Sukumaran.

“Any delay in plans by the Indonesian authorities to execute Mr Chan and Mr Sukumaran will be a relief to the men and their families, Bishop told the ABC on Wednesday.

“It gives us an opportunity to continue to engage on the best way forward with the Indonesian authorities so we will continue our representations at the highest level across the Indonesian government.

The opposition leader, Bill Shorten, said the delay provided “a modest opportunity for people to engage in constructive suggestions and discussion aimed at preventing the executions.

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