Nguyen Tuong Van, a Melbourne resident of Vietnamese origin, is headed for the gallows after Singapore President S R Nathan's rejection of clemency appeals by the Australian government.
Executions are carried out on Fridays in Singapore, triggering
speculation that Nguyen's death could be imminent.
Singapore officials have a policy of not announcing hangings in advance.
"He was given a fair hearing throughout the legal process and
his appeal for clemency was carefully considered," Singapore's High Commissioner to Australia Joseph Koh said in a statement.
"After taking into account all factors, the president, on the
advice of the cabinet, was unable to make an exception to Mr Nguyen's case.
"I understand that this decision is difficult for his family to
accept. But the stand the government has taken on Mr Nguyen is consistent with the firm position that Singapore has taken on similar cases in the past involving Singaporeans and foreigners alike.
"Not everyone may agree with our view, but I hope they will
understand Singapore's position."
Nguyen was sentenced to die for smuggling 400 grams (14 ounces) of heroin into Singapore in 2002. He told police he was smuggling the drugs to Australia to help pay off a debt owed by his twin brother.
"Our policy has been well-publicised and Mr Nguyen was well aware of it"
Joseph Koh, Singapore High Commissioner to Australia
Australia, where capital punishment is outlawed, had lobbied for months against his execution.
Sydney's Catholic Archbishop Cardinal George Pell has also asked Pope Benedict XVI to intervene to save Nguyen's life.
But Singapore's High Commissioner Koh said in the statement that his country takes a serious view of all drug offences.
"We weigh the rights of offenders against the rights of victims and the rights of the community to live and work in safety and security.
"Our strict anti-drug laws send a clear message to drug
syndicates not to conduct their criminal activities in Singapore or through Singapore. Our policy has been well-publicised and Mr Nguyen was well aware of it."