Ukrainian President Volodymyr Zelensky will meet the King as part of his visit to the UK, the PA news agency understands.
Mr Zelensky is due to speak to Charles on Sunday, the same day as Sir Keir Starmer’s defence summit of European leaders in London.
It will take place at Sandringham, The Sun newspaper reported.
The pair met during Mr Zelensky’s surprise visit to the UK in February 2023, when the King told him “we’ve all been worried about you and thinking about your country for so long”.
Mr Zelensky used his address to Parliament during that visit to thank the UK for its steadfast support, finishing by saying “God bless Great Britain and long live the King”.
They also shook hands and had a private summit at the European Political Community summit in Oxfordshire in July 2024.
They met during the European Political Community summit at Blenheim Palace in Woodstock, Oxfordshire (Hollie Adams/PA)
Their latest meeting will come after Mr Zelensky’s unprecedented public clash with US President Donald Trump and his vice president JD Vance in the White House’s Oval Office on Friday.
A day prior, Charles invited Mr Trump to the UK for an unprecedented second state visit.
The Prime Minister handed him a letter from the King on Thursday as the two were facing cameras ahead of the more in-depth talks in Washington.
Mr Trump showed the letter marked “private and confidential” and featuring Charles’s signature to the cameras gathered in the White House.
The King suggested that he and Mr Trump could meet before that visit, either at Dumfries House or Balmoral which are near the businessman’s golf courses in Scotland, to discuss the plans for the much grander state visit.
US President Donald Trump is presented with a letter from the King (Carl Court/PA)
The letter, partially obscured by Mr Trump’s hand, read: “I can only say that it would be … pleasure to extend that invitation once again, in the hope that you … some stage be visiting Turnberry and a detour to a relatively near neighbour might not cause you too much inconvenience.
“An alternative might perhaps be for you to visit Balmoral…
“There is much on both estates which I think you might find interesting, and enjoy – particularly as my foundation at Dumfries House provides hospitality skills training for young people who often end up as staff on your own establishments!”
The US president claimed Mr Zelensky was “gambling with World War Three” in a series of heated exchanges on Friday which were broadcast around the world.
The Ukrainian leader was also accused of not being thankful enough for US military aid by both the US president and his deputy Mr Vance.
The meeting ended with Mr Zelensky reportedly being kicked out of the White House, and plans to sign a deal exchanging Ukrainian mineral rights for American arms were put on ice.