The Queen and the Duke of Sussex are to hold talks at Sandringham on Monday to discuss the future roles of Prince Harry and the Duchess of Sussex.
Palace officials have also told the BBC the Prince of Wales and the Duke of Cambridge are expected to attend the meeting.
The Sussexes say they plan to step back as senior members of the royal family.
There is no suggestion that a conclusion will be reached at the meeting.
But it is hoped that the talks will produce a “next step” on the way to defining the couple’s new relationship with the Royal Family – in line with the Queen’s wish to find a solution within days.
He added that there were still “formidable obstacles” to overcome in the talks.
Monday’s gathering at the Queen’s estate in Norfolk follows several meetings and consultations in the wake of the couple’s announcement earlier this week.
Posted on their Instagram page, Prince Harry and Meghan said they intended to “step back” as senior members of the Royal Family and work to become financially independent.
The Queen, Prince Charles, William and Harry are expected to review a range of possibilities for the Sussexes, taking into account the plans outlined by Prince Harry and Meghan.
If a deal is agreed in the coming days, there is a general understanding that it will take some time to implement.
Monday’s royal summit may not be the last such gathering needed to sort things out; but enough progress has been made by palace staff and civil servants for the most senior members of the family to meet to discuss some pretty concrete proposals on the way ahead for Prince Harry and Meghan.
There are still formidable obstacles – it’s not at all clear how much in the way of royal duties the prince and Meghan see themselves doing.
On that will hang issues such as funding and liaison between the palace and Prince Harry and Meghan’s new organisation. Unpicking the current relationship is complicated – creating a new one, that lasts, will be even tougher.
There’s a strong desire to get this done. But equally the deal must be robust and workable.
Precedent is being established here – a way of doing things that may extend in years to come to other members of the royal family.
Meghan returned to Canada to join her son Archie amid the ongoing talks, which have involved the UK and Canadian governments.
She and Prince Harry had been in Canada over Christmas, before they returned to the UK on Tuesday after a six-week break from royal duties.
On Friday, the couple’s official Instagram account returned to publicising their appearances.
In their announcement on Wednesday evening, Prince Harry and Meghan revealed they plan to split their time between the UK and North America, while “continuing to honour our duty to the Queen, the Commonwealth, and our patronages”.
The Royal Family was said to be “hurt” at the couple’s announcement. It is understood the Queen was not consulted in advance of their decision.
Last October, Prince Harry and Meghan publicly revealed their struggles under the media spotlight.
Former actress Meghan, who is American, lived and worked in Toronto where she starred in the popular US drama Suits.
The couple were already preparing to launch their own Sussex Royal charity, which they set up after splitting from the Duke and Duchess of Cambridge’s foundation in June last year.
It was revealed in December the couple had made an application to trademark their Sussex Royal brand across a string of items including books, calendars, clothing, charitable fundraising, education and social care services.