President Donald Trump's youngest brother Robert is said to be ‘very ill’ in a New York City hospital.

White House press secretary Kayleigh McEnany confirmed the hospitalisation to ABC News, adding that the president and his brother ‘have a very good relationship’ and that the president would be providing more details later.

Trump is expected to visit his brother, one of his four siblings, according to a senior administration official. He's already scheduled to visit his nearby country club in Bedminster, New Jersey, on Friday and deliver remarks to the City of New York Police Benevolent Association.

Robert, 72, spent more than a week in the intensive care unit at Mount Sinai Hospital in June. 

He formerly served as an executive for the Trump Organisation and is currently based in Long Island where he lives with wife Anne Marie Pallan.

He was recently involved in a legal battle against niece Mary Trump, the daughter of Fred Trump Jr, to block her from publishing a tell-all book on the President.