Australia has offered to cover the cost of life imprisonment for Bali Nine drug smugglers Andrew Chan and Myuran Sukumaran if appeals for clemency, a permanent stay of execution or a one-off prisoner transfer fail.
Foreign Minister Julie Bishop made the offer to Indonesian counterpart Retno Marsudi in a letter obtained by The West Australian.
In her letter, Ms Bishop lists the alleged corruption of trial judges as one of many reasons for the two Australians' executions to be stopped.
"There are compelling grounds for a permanent stay of execution, given the irreversibility of capital punishment," Ms Bishop told Ms Marsudi in the March 5 letter.
The outcome of a challenge to President Joko Widodo's refusal to grant clemency to Chan and Sukumaran will be known today.
Ms Bishop's letter indicates Australia will not regard an unfavourable decision of Indonesia's State Administrative Court as final. "A Judicial Commission has invited Mr Chan, Mr Sukumaran and their original lawyer to make statements in a matter relating to alleged corruption of the trial judges," Ms Bishop wrote.
"These are serious allegations and I request that your Government accord due legal process and institute a pause in the execution preparations."
Behind the scenes, Australian Government contacts have engaged with military hardman and one-time Indonesian presidential candidate Prabowo Subianto to explore what influence he could bear on preventing the executions.
Diplomatic tensions have increased in recent days, with one Indonesian minister warning that Australia would be inviting retribution if it responded to the executions with foreign aid cuts or travel bans to Bali.
Indonesia's Co-ordinating Minister for Political, Legal and Security Affairs Tedjo Edhy Purditjatno reminded Australia of the 10,000 asylum seekers residing in Indonesia.
"Imagine if we let them all go to Australia," he said.
Ms Bishop offered to institute a one-off prisoner transfer agreement - three convicted Indonesians in exchange for Chan and Sukumaran.
"There are Indonesian prisoners in Australian prisons, arrested by Australian police for seeking to import 390 kilograms of heroin into Australia - 47 times the amount that Mr Chan, Mr Sukumaran and their co-convicted sought to smuggle from Indonesia to Australia," Ms Bishop wrote.
"As discussed, the Australian Government would be prepared to cover the costs of the ongoing life imprisonment of Mr Chan and Mr Sukumaran should a transfer not be possible."
Ms Bishop emphasised the prisoners' deep remorse and "remarkable transformation".
"We would not want to see their execution compromise the strong ties we have worked so hard to foster over many years," she wrote.
Ms Marsudi's letter in response, received on Sunday, was polite but comparatively short.
"Let me reiterate that there is no legal basis within the Indonesian law that would allow for such exchange to take place," Ms Marsudi told Ms Bishop.
"I have also conveyed your concerns to President Joko Widodo.
"The President is of the position that such an exchange cannot be undertaken."
Yesterday, Chan spent time with his fiancee Febyanti Herewila, his mother Helen and two close family friends.
Sukumaran was visited by his mother Raji, brother Chintu, sister Brintha and a cousin.
Chintu Sukumaran said the family remained hopeful Mr Joko would see the work his brother had done to rehabilitate inmates in Kerobokan jail and have mercy on him and Chan.
"We're grateful to the Indonesian justice system for this and all we ask is that they be able to spend the rest of their life in prison and not be executed," he said.
The Grand Mufti of Australia, Ibrahim Abu Mohammed, visited Jakarta yesterday, encouraging Indonesian Islamic leaders to consider mercy for Chan and Sukumaran.
Dr Abu Mohammed met Religious Affairs Minister Lukman Hakim Saifuddin, telling him Australia's Islamic leaders respected the Indonesian Government's firm pursuit of drug crime and made no criticism of the justice system. "However, we note that mercy and forgiveness lies at the heart of Islam for those who repent and have reformed their ways," he said.