WASHINGTON (BLOOMBERG) - The Nelson Mandela Foundation criticised reported remarks by United States President Donald Trump that denigrated the former South African leader.

The Washington Post reported on Sunday (Sept 6) that Michael Cohen, Mr Trump's former lawyer and personal fixer, alleged in a new book that the US President did not think Mr Mandela was a real leader and that South Africa had deteriorated under his rule.

The Washington Post said Mr Trump also praised the country's apartheid-era rule.

"We do not believe that leaders who conduct themselves in the way Mr Trump does are in a position to offer authoritative commentary on the life and work" of Mr Mandela, the foundation said in a statement on its website.

Cohen, who was an intimate witness to Mr Trump's business dealings, has fallen out with the President since pleading guilty in 2018 to financial fraud and lying to Congress.

The Washington Post obtained a copy of Cohen's book, Disloyal: A Memoir, in advance of its publication on Tuesday.

Mr Trump's spokesman issued a blanket denial of the book at the weekend.

Mr Mandela was South Africa's first black president from the end of white-minority rule in 1994 until 1999. He died in 2013.

In its statement, The Mandela Foundation cited a quote by the former president on leadership: "A good leader can engage in a debate frankly and thoroughly, knowing that at the end he and the other side must be closer, and thus emerge stronger. You don't have that idea when you are arrogant, superficial, and uninformed."

"We would recommend these words to Mr Trump for consideration," the foundation said.

South Africa's Department of International Cooperation and Development didn't immediately respond to calls and messages seeking comment.