Sinn Fein's Martin McGuinness has announced he is quitting frontline politics to concentrate on recovering from "a very serious illness".
Mr McGuinness resigned as Northern Ireland's deputy first minister last week in protest against the handling of a botched energy scheme, forcing a snap election.
He has now revealed that after "a lot of thinking" he will not be contesting those elections due to ill health.
"The question I asked myself was 'are you physically capable of fighting an intensive 5/6 week election and doing it to my full abilities?' I rapidly came to the conclusion that I am not in any physical state to fight such a campaign. So I have taken the decision that I will not be a candidate in the upcoming election," he said.
Mr McGuinness said he had intended to stand aside in May, on the 10th anniversary of going into government with the DUP's Ian Paisley.
However, he said that the DUP's handling of the Renewable Heating Initiative (RHI) scandal left him with "no other alternative" but to resign earlier this month.
DUP leader Arlene Foster's refusal to step aside pending an interim report into the scheme was her "biggest mistake", Mr McGuinness said.
"God knows where it is all going to end. But quite clearly at the heart of it is a very clear perception of not just incompetence, but allegations of corruption are flying all over the place. That was an intolerable situation for me to find myself in."
"As someone who has worked night and day over the course of 10 years to keep the institutions intact, and of course many conversations with both the British and Irish Government about the DUP, it was particularly disappointing having kept up the institutions for almost 10 years that I found myself with no other alternative but to resign. And of course that has led to an election."
The former deputy first minister told the Press Association he has been battling ill health for several months, but he hopes to make a recovery.
"On medical advice last year I was advised not to travel to China and in the aftermath of that I underwent a whole series of tests. As a result of those tests I have been diagnosed with a very serious illness which has taken a toll on me.
"But I am being cared for by wonderful doctors and nurses within our national health service and I am very determined to overcome this condition but it is going to take time."
Mr McGuinness said a new candidate to lead the party into the elections will be announced next week.
He added that although his electoral career is now at an end, his political career is not.
"I hopefully will overcome this illness through time. I am very determined to be an ambassador for peace, unity and reconciliation.
"Reconciliation, I have always believed, is the next vital stage of the peace process.
"My record of reaching out, whether it be to Queen Elizabeth - and her record of reaching out to me on several occasions - my visits to the Somme, to Flanders field, have not been reciprocated by the DUP and that is a particular disappointment to me."