DONALD Trump said Prince William told him King Charles is "fighting very hard" - and Princess Kate is "doing well" as the pair met in Paris.
The Prince of Wales, 42, travelled to the French capital on Saturday for the ceremonial reopening of Notre Dame cathedral following a devastating fire in 2019.
After it ended, he went to the residence of the British ambassador for a meeting with Mr Trump.
Mr Trump, 78, later revealed more about their conversation in an interview with the .
The pair discussed Charles and the Princess of Wales' health, after both were diagnosed with cancer this year.
He said: "I had a great talk with the prince. And I asked him about his wife and he said she's doing well.
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"And I asked him about his father and his father is fighting very hard, and he loves his father and he loves his wife, so it was sad."
Mr Trump also said William was "very handsome" adding "some people look better in person".
Mr Trump continued: "We had a great talk for half an hour, a little more than half an hour. We had a great, great talk.
"He's a good looking guy. He looked really, very handsome last night. Some people look better in person?
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"He looked great. He looked really nice, and I told him that."
The Palace announced King Charles had been diagnosed with an undisclosed form of cancer in February.
Kate is making a gradual return to public events after completing her cancer treatment around four months ago.
Earlier the pair shook hands and greeted one another before Mr Trump turned to reporters and said "wow, what a nice group".
He then gestured to the prince and said: "Good man, this one."
William asked the president-elect if he had warmed up after the event.
Mr Trump replied that he had and that "it was a beautiful ceremony".
The two men stood next to each other, facing reporters, and Mr Trump said "hello everybody" before pointing his thumb at William and adding: "He's doing a fantastic job".
In the cathedral, Mr Trump gave William a pat on the shoulder before they shook hands.
The prince last met the 78-year-old in 2019 when the then-president made a state visit to the UK.
William received a warm greeting in the rainy French capital from President Emmanuel Macron and his wife Brigitte Macron.
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IT is great to see Prince William gradually emerging as Britain's head of state in waiting.
He showed maturity and poise when representing Britain and meeting incoming US President Donald Trump at the reopening of Notre Dame cathedral.
The Prince was due to stress the importance of the Special Relationship between the US and Britain.
The message could hardly be more timely given the uncertainty around Mr Trump's foreign and trade policies.
King Charles will, of course, play the key role as monarch in any state visit by the US President.
A perfect opportunity for this will fall when Mr Trump travels to a NATO summit in the Hague in June.
Yet the Prince's growing confidence in filling in for his father on such sensitive occasions is reassuring.
Sir Keir's own Cabinet ministers have an embarrassing past history of criticising Mr Trump.
So the PM must count himself lucky he has such excellent royal ambassadors for Britain on his side.
The prince also spoke to America's outgoing first lady Jill Biden at the ceremony.
He was expected to discuss the importance of the US-UK relationship with Mr Trump and Mrs Biden.
His last official visit to Paris was in 2017 when he travelled with wife Kate for a two-day trip in the aftermath of the Brexit result.
Earlier this year, he joined world leaders in Normandy for the 80th anniversary commemorations of the Second World War D-Day landings.
Notre Dame's reopening included the ritualised opening of the cathedral's massive doors, the reawakening of its thunderous organ and the celebration of the first Mass.
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Tickets for the first week of Masses were snapped up in 25 minutes, the cathedral's rector said.
On Sunday, an inaugural Mass was held featuring special rites to consecrate the main altar.
Secrets of the £1billion restoration
By Ryan Parry
IT took more than 200 years to build the Notre Dame Cathedral — and just a few hours for a raging inferno to almost destroy it in 2019.
Hours after the devastating blaze, President Emmanuel Macron vowed to rebuild the Gothic masterpiece within five years.
It started a mind-boggling £1billion restoration project, with more than 1,600 tons of scaffolding going up.
More than 1,000 craftsmen and 2,000 labourers have worked around the clock to restore the cathedral.
Builders used 1,200 oak trees from 200 French forests to recreate the roof's mammoth frame.
It had to support 4,000 square metres of lead weighing 210 tons.
More than 1,000 pieces of wood were also used to rebuild the 96-metre spire, first erected in 1859, with the largest pieces up to 12 metres long.
Using techniques not used for such a major build in centuries, 60 timber hewers and carpenters replicated the intricate medieval architecture.
Around 1,000 cubic metres of new stone were needed to renovate the vaults.
The Grand Organ's 8,000 pipes were also dismantled, cleaned and restored, taking eight months.
A similar process took place with the bells in the north tower — no mean feat as the biggest weighs four tons.
President Macron declared last month on a visit: "You have achieved what was thought impossible."