The King has sent a personal message of congratulations to Donald Trump on his inauguration, reflecting on the enduring special relationship between the UK and US, Buckingham Palace said.
Charles’s private written words were delivered to mark Mr Trump being sworn into office as US president for a second time.
It is understood all options remain possible for an incoming state visit visit by Mr Trump to the UK and a visit by Charles to the US, but no plans are currently in the diary.
Foreign monarchs, presidents or prime ministers are invited to visit the King on the advice and request of the Foreign and Commonwealth Office, with the decision down to the Government.
With the Republican politician making the most dramatic comeback in US political history, Charles and Mr Trump will be expected to encounter one another face to face once again during Trump 2.0, as his second term in office is being dubbed.
Mr Trump is well known for his love of the monarchy and the royal family plays a central role in the UK’s bond with the US.
The US leader boasted he had “automatic chemistry” with the late Queen, and has hailed the King as a “really wonderful guy”.