Fr William Aitcheson from Virginia said he felt compelled to speak out about his "despicable" past after a recent white supremacist rally in the US state which turned deadly.
In a column published by the Arlington Catholic Herald, the 62 year old said: "While I firmly believe God forgave me, as he forgives anyone who repents and asks for forgiveness, forgetting what I did would be a mistake.
"My actions were despicable. When I think back on burning crosses, a threatening letter, and so on, I feel as though I am speaking of somebody else."
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Violence broke out at a racist gathering in Charlottesville on Saturday 12th August when counter-protestors confronted demonstrators. A 32-year-old woman died when a car ploughed into the counter-protestors.
Urging white supremacists to repent and seek forgiveness, Fr Aitcheson said: "You will find no fulfilment in this ideology," he wrote. "Your hate will never be satisfied and your anger will never subside."
Amid the article's publication, Arlington Diocese noted he had voluntarily sought to temporarily step aside from public ministry, "for the wellbeing" of Church and parish community. His racist past was not widely known in the diocese.
Fr Aitcheson was sentenced to 90 days in jail after being charged in 1977 with multiple cross-burnings and threatening to kill with the widow of Martin Luther King Jr.
Five years later, he was told by a judge to pay damages totalling $23,000 to two people targeted in one of his cross-burnings in Maryland.
Arlington Bishop Michael Burbidge said he hopes Fr Aitcheson's story will encourage transformation in others.
He also expressed confidence in Fr Aitcheson's change of heart was sincere, "evidenced, in part, by the fact that we have had no accusation of racism while ministering".
He added: "I pray that in our current political and social climate his message will reach those who support hate and division, and inspire them to a conversion of heart."