"The practical arrangement will be signed today. The transfer will be done immediately after the technical side of the transfer is agreed," the source said, identifying Lindsay Sandiford and 35-year-old Shahab Shahabadi as the people being transferred.

Sandiford, a grandmother, was sentenced to death on the island of Bali in 2013 after she was convicted of trafficking drugs.

Customs officers found cocaine worth an estimated $2.14 million hidden in a false bottom in Sandiford's suitcase when she arrived in Bali on a flight from Thailand in 2012.

Shahabadi was arrested in 2014 on drug charges and is currently serving a life sentence, according to information shared by the source.

The government source listed Sandiford as 68 years old, though public information showed her to be 69.

The British embassy in Jakarta directed all queries to the Indonesian government.

A press conference for the "release of two British nationals" was scheduled for later Tuesday by Indonesian authorities and the British ambassador to Indonesia, according to a release by the Coordinating Ministry for Legal, Human Rights, Immigration and Correction.

Sandiford admitted the offences but said she had agreed to carry the narcotics after a drug syndicate threatened to kill her son.

Indonesia has some of the world's toughest drug laws, and dozens of foreigners remain on death row for drug offences there.

Sandiford's case caught tabloid attention back home in Britain, with one newspaper publishing an article written by her in which she detailed her fear of death.

"My execution is imminent, and I know I might die at any time now. I could be taken tomorrow from my cell," she wrote in British newspaper the Mail on Sunday in 2015.

"I have started to write goodbye letters to members of my family."

Sandiford, originally from Redcar in northeast England, wrote in the article that she had planned to sing the cheery Perry Como hit "Magic Moments" when facing the firing squad.

She became friends in prison with Andrew Chan, an Australian killed by firing squad for his role in a plan to smuggle heroin as one of the so-called "Bali Nine" group of smugglers.

President Prabowo Subianto's administration has moved in recent months to repatriate several high-profile inmates, all sentenced for drug offences, back to their home countries.

In December, Filipina inmate Mary Jane Veloso tearfully reunited with her family after nearly 15 years on death row.

In February, French national Serge Atlaoui, 61, was returned home after 18 years on death row in Indonesia.

Indonesia last carried out executions in 2016, killing one of its own citizens and three Nigerian drug convicts by firing squad.

Indonesia's immigration and corrections ministry said more than 90 foreigners were on death row, all on drug charges, as of early November.

The Indonesian government recently signaled it could resume executions.