President Donald Trump, who began his weekend by visiting his ailing brother Robert in a New York hospital before heading off to his golf club in New Jersey, announced Saturday that his "best friend" had died after an undisclosed illness.

"It is with a heavy heart I share that my wonderful brother, Robert, peacefully passed away tonight," Trump said in a statement.

Robert Stewart Trump was born in 1948, the youngest of the five children of New York City real estate developer Fred Trump.

In June, Robert Trump had sought a restraining order against his and the president's niece, Mary Trump — at a moment when ABC News reported that the younger Trump had been hospitalized in intensive care.

Read more: Mary Trump's book about the president a bestseller

Her book, published in July after a judge lifted the temporary order, depicts the president in highly unflattering terms.

'We will meet again'

Reuters quoted an aide of the president as saying that Trump would attend the funeral amid a busy schedule in coming days, including reelection campaign visits to four highly contested states.

Read more: Trump moots US election delay on Twitter

Trump, in his Saturday statement, said his brother would be "greatly missed, but we will meet again."

"His memory will live on in my heart forever. Robert, I love you. Rest in peace," said Trump.

Trump once described his brother as "much quieter and easygoing than I am" and "the only guy in my life whom I ever call honey."

Beginning his career on Wall Street in corporate finance, Robert Trump later joined the family business. He avoided the limelight during his elder brother's presidency.

Read more: US Postal Service: Mail-in votes may not be counted in time for election

ipj/shs (Reuters, AP)