Indonesia has delayed the execution of two Australian drug smugglers by up to a month, backtracking on an earlier pledge to put the pair before the firing squad by the end of February.

Vice President Jusuf Kalla's office Friday said the execution of Andrew Chan and Myuran Sukumaran, the ringleaders of the so-called "Bali Nine" heroin trafficking group, "will be delayed for between three weeks to a month from now due to technical reasons," without elaborating further.

Indonesian authorities insist they will proceed with the executions despite this delay.

Indonesian president Joko Widodo -- an ardent supporter of the death penalty who has refused clemency for the two Australians -- denied pressure from Australia had swayed his resolve to see drug traffickers executed.

"No such thing," he told reporters on Friday. "This is our judicial sovereignty."

Canberra has been ramping up diplomatic pressure in recent weeks for the pair to be spared, straining ties between the two countries, but analysts say public perception will guide Widodo far more than pleas for mercy from Australia.

Widodo has shocked rights groups with his support for capital punishment for drug dealers, vowing he won't grant clemency to anyone caught selling narcotics to his countrymen.

Hikmahanto Juwana, an international law professor from the University of Indonesia, said the majority of Indonesians shared Widodo's tough stance on traffickers and expected him to tackle the "drug emergency" facing the country.

"He should not back down because it was causing an uproar in Australia," he told AFP.

"If he backs down, he will face the Indonesian public."


'Logistical difficulties'

This month, Indonesia's foreign ministry informed the Australian embassy that the execution of the two drug convicts would be carried out in February.

But since then it has announced, and subsequently backtracked, on details of the executions plan for Chan and Sukumaran.

On Monday it was announced the pair would be transferred this week from Bali to a high-security prison on Nusakambangan -- signalling a date for their execution was near -- only for that decision to be reversed 24 hours later.

Indonesia said it delayed their transfer because of logistical difficulties at Nusakambangan -- the notorious island prison where five inmates were shot last month -- with facilities at the execution site already at capacity.

Tony Spontana, a spokesman for the attorney-general's office which oversees the executions, said once the prison was ready to receive the prisoners the executions would proceed.

"What needs to be underscored is the execution will still be conducted," he told AFP after the postponement was announced Friday.

He has said previously the prisoners would only be taken to Nusakambangan three days before their execution. Death row inmates must be given 72 hours' notice under Indonesian law before facing the firing squad.

Indonesia also claimed they delayed the transfer because Australia had requested the men be granted more time with their families, but denied Jakarta was bowing to pressure from Canberra.


International pressure

Indonesia's pledge to proceed with the execution of the Australians has hiked tensions between Jakarta and Canberra, a relationship only just recovering from a damaging rift in 2014 over spying revelations and people-smuggling.

Aleksius Jemadu, a political expert at Indonesia's Pelita Harapan University, said arm-twisting by Australia would not be at the front of Widodo's mind as he mulls this issue.

"The president is very much influenced by his image as a populist president," he told AFP.

"His government (by proceeding with the executions) will be considered a brave one which cannot be dictated to by foreigners, and is independent in decision making."

Diplomatic tensions boiled over this week after Prime Minister Tony Abbott said Indonesia should remember the significant financial aid Australia provided in the aftermath of the devastating 2004 tsunami that killed 170,000 Indonesians.

Abbott denied the comment was threatening, but Indonesia's Foreign Minister Retno Marsudi on Friday suggested Jakarta felt otherwise.

"We will not respond to an emotional statement, which was a threat in nature," she said, adding she did not think Indonesia owed Australia anything for their tsunami aid.

Australia's foreign minister Julie Bishop rang Kalla on Thursday to explain the "misunderstanding", the vice-president told reporters Friday.

Indonesia executed six drug offenders in January, including five foreigners, prompting a furious Brazil and the Netherlands -- whose citizens were among those put to death -- to recall their ambassadors.

Chan and Sukumaran are among seven foreigners -- including citizens from France, Ghana, Brazil and Nigeria -- who have already lost their appeals for presidential clemency, the final hope of avoiding the firing squad.

Lawyers for the Australians have lodged a rare legal challenge to the president's decision to reject clemency, but Indonesian authorities have repeatedly said the appeal for a pardon is a death row convict's final chance to avoid the firing squad.