"Some wounds are too deep to be healed even by the remedy of time," Harper wrote in his speech which he prepared for the occasion.
"We are sorry," Canadian Broadcasting Corporation (CBC) said quoting the Prime Minister.
"Harper will say the destruction of Air India Flight 182 'was, and remains, the single worst act of terrorism in Canadian history,'" the national broadcaster reported.
"He will describe terrorism as 'an enemy with a thousand faces, and a hatred that festers in the darkest spots of the human mind,'" it added.
"This was evil, perpetrated by cowards. Despicable, senseless and vicious," Harper will say.
The Canadian premier had promised to respond positively to the damning report into the 1985 Kanishka bombing, especially on the call for compensation, as the families torn apart by the tragedy said the word "closure" still haunts them.
The final report into the Air India tragedy that killed 329 people recommended ex-gratia payment to families of victims, mostly of Indian-origin, and blamed the Canadian
government for its failure to prevent the country's worst terror attack.
Soon after the report's release, Harper met the families and termed the document a "damning indictment of many things that occurred before and after the tragedy".
"Our government launched this inquiry to bring closure to those who still grieve and to ensure that measures are taken to prevent such a tragedy in the future," he had said.
Inderjit Singh Reyat, the only person ever convicted in the case, pleaded guilty to manslaughter in 2003. Suspected ringleader Talwinder Singh Parmar died in
India in 1991, and the two main surviving suspects Ripudaman Singh Malik and Ajaib Singh Bagri were both acquitted in March 2005 after a 19-month trial.
British Columbia Supreme Court Justice Ian Josephson had ruled that the Crown's case against the two was too weak for a conviction.
Toronto: Canadian Prime Minister Stephen Harper will convey a heartfelt message today to families of the victims of the Kanishka bombing on the 25th anniversary.
First Published: Wednesday, June 23, 2010, 09:42