Buckingham Palace has warned the from the royal family will be "complicated" and talks are still at an early stage.
It is understood that the Queen and the Prince of Wales were not aware of the content of before it was issued.
The couple's decision was announced on Wednesday evening when they said they will work to become financially independent while continuing to "fully support" the Queen.
But a palace spokeswoman said: "Discussions with The Duke and Duchess of Sussex are at an early stage.
"We understand their desire to take a different approach, but these are complicated issues that will take time to work through."
The couple's move follows weeks of speculation about their future after they took an extended break from royal duties over the festive period.
: "After many months of reflection and internal discussions, we have chosen to make a transition this year in starting to carve out a progressive new role within this institution.
"We intend to step back as 'senior' members of the Royal Family and work to become financially independent, while continuing to fully support Her Majesty The Queen.
"It is with your encouragement, particularly over the last few years, that we feel prepared to make this adjustment.
"We now plan to balance our time between the United Kingdom and North America, continuing to honour our duty to The Queen, the Commonwealth, and our patronages.
"This geographic balance will enable us to raise our son with an appreciation for the royal tradition into which he was born, while also providing our family with the space to focus on the next chapter, including the launch of our new charitable entity.
"We look forward to sharing the full details of this exciting next step in due course, as we continue to collaborate with Her Majesty The Queen, The Prince of Wales, The Duke of Cambridge and all relevant parties. Until then, please accept our deepest thanks for your continued support."
*Additional reporting by PA.
