Thomas Markle said he will go into surgery at 7.30am in Mexico, where he lives, after he reportedly suffered from a heart attack last week.
He will not be able to travel to England for his daughter’s wedding to Prince Harry on Saturday in Windsor, celebrity website TMZ said.
His absence most likely means that his ex-wife, Meghan’s mother Doria Ragland, will walk their daughter down the aisle at St George’s chapel in the grounds of Windsor Castle.
Mr Markle, 73, is believed to have started having chest pains on Monday and checked himself into hospital on Tuesday where he had a series of tests.
“They [doctors] will go in and clear blockage, repair damage and put a stent where it is needed,” he told TMZ.
He said the heart attack did significant damage – and he claimed an open letter from his son, Thomas Jr, wrote to Prince Harry discouraging him from marrying Meghan triggered his heart attack, TMZ said.
Mr Markle’s presence at the wedding had been the source of speculation since he allegedly staged paparazzi photographs of himself getting measured for a suit for the wedding and browsing news websites for stories on his daughter.
On Monday he reportedly said he would not be going to the wedding, telling TMZ that he did not want to “embarrass the Royal Family or his daughter”.
Then, earlier on Tuesday, he said he had changed his mind and was hoping to walk Ms Markle down the aisle, saying he would hate to miss out on a historic day.
“I hate the idea of missing one of the greatest moments in history and walking my daughter down the aisle,” he had told TMZ.
“This is a historic moment. I’d like to be a part of history.”
TMZ said Ms Markle had tried calling him on Monday and sent him a text saying she loved him and was concerned about his health.
Mr Markle told TMZ that Meghan had said she does not have any ill feelings towards him for staging the photos.
He said that after thinking about the situation the incident was not a “serious transgression”, but simply “stupid”.
Kensington Palace has neither confirmed or denied whether Mr Markle will attend, but has appealed for understanding.
A spokesman said earlier: “This is a deeply personal moment for Ms Markle in the days before her wedding.
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“She and Prince Harry ask again for understanding and respect to be extended to Mr Markle in this difficult situation.”
:: Sky News will broadcast live in Windsor the week before the royal wedding with all the build-up to the big day, with exclusive live coverage of the wedding in UHD in a special programme from 9am to 3pm on Sky News and Sky One on Saturday 19 May.