US President Donald Trump has said he believes people with learning disabilities should not be president, as he renewed his taunts at California Governor Gavin Newsom over his dyslexia.
Trump said Newsom, a potential Democratic White House contender, was "dumb". The California governor last week called Trump "a brain-dead moron" after he made fun of his difficulty with reading and spelling words.
The National Center for Learning Disabilities told the BBC it was "disturbed by and strongly condemns" the Republican president's remarks.
Dyslexia, a learning condition that disrupts how the brain processes written language, affects as many as one in five Americans.
"With a low IQ person, you know, because Gavin Newscum has admitted that he is a, that he has learning disabilities," Trump told reporters in the Oval Office on Monday. "Newscum" is Trump's nickname for the governor.
"Honestly, I'm all for people with learning disabilities, but not for my president. I don't want, I think a president should not have learning disabilities, OK? And I know it's highly controversial to say such a horrible thing."
He added: "The President of the United States, Gavin Newscum, admitted that he has learning disabilities, dyslexia. Everything about him is dumb."
Newsom made fun of Trump on social media for accidentally calling him the president of the United States. "NO THANK YOU, WE BELIEVE IN FREE ELECTIONS!" the California governor wrote.
At a conversation last month with the mayor of Atlanta, Georgia, Newsom discussed his dyslexia.
"I'm like you," the governor told the audience as he cited his poor exam results and difficulty reading.
"You've never seen me read a speech, because I cannot read a speech," he added.
His remarks to a predominantly black audience sparked a chorus of conservative claims that he was talking down to African-American voters.
Trump also accused Newsom of racism and posted on Truth Social that he "can't read, has dyslexia, and has a mental disorder - A Cognitive Mess!"
Newsom shot back at Trump on social media, saying: "I spoke about my dyslexia."
"I know that's hard for a brain-dead moron who bombs children and protects pedophiles to understand."
The National Center for Learning Disabilities said in a statement to the BBC on Monday that dyslexia does not impair a person's intelligence, judgment or ability to lead.
The centre's chief executive, Jackie Rodriguez, said: "In fact, people with learning disabilities have risen to the upper echelon of every public office in the United States, including former Presidents."
Past US presidents, including George Washington, John F Kennedy and Woodrow Wilson, may have had dyslexia, according to some researchers.
About 15% of the US population is affected by dyslexia, according to the US Department of Health and Human Services. Some estimate the figure may be as high as 20%.