Prince Harry is expected to call King Charles III on his 75th birthday to wish him well.
But the Duke of Sussex and his family will not travel to London where his father is holding a small celebratory gathering at Clarence House this evening, according to Mail Online.
The King's 75th birthday will be a working day for the monarch marked by gun salutes across the capital.
Charles will also officially launch the Coronation Food Project with the Queen which aims to bridge the gap between food waste and food need.
A 'well-placed' source told the BBC that Harry would want to speak to his father on his big day.
The King is expected to celebrate his milestone birthday privately with family and friends tonight.
At noon, the King's Troop Royal Horse Artillery, named after Charles's grandfather King George VI, will fire a 41-gun salute from London's Green Park. An hour later, the Honourable Artillery Company will fire a 62-gun salute at Tower Wharf, Tower of London - an extra 21 for the City of London.
Last week Harry re-ignited his public war of words with the Royal Family when reports said he declined to attend the King’s 75th birthday celebrations.
His spokesman denied reports that Harry snubbed an invitation to a Clarence House family gathering tonight, saying: ‘There has been no contact regarding an invitation to His Majesty’s upcoming birthday.’
A ‘source close to the Sussexes’ told the Mail the couple were not aware the King was holding a celebration until The Sunday Times made the claim.
The paper reported that the King invited Harry but that the Duke of Sussex ‘is not making the trip from California’. It also said he had ‘turned down the offer to spend some time with his father at Balmoral’ over the summer.
But it appears there will be an olive branch later today, with a phone this afternoon or evening due to the time difference in California.