The Democratic candidate, Vice President Kamala Harris (left) and the Republican candidate, former President Donald Trump (right) (Photo: AP/Vietnam News Agency)

The candidates will not be allowed to bring notes and will have to stand during the entire debate, said Trump, adding that ABC News has assured him of a fair and equitable debate, where neither side will know the questions beforehand. The Republican candidate said he is also open to two other debates in September, although Kamala Harris has not commented on that possibility.

Trump suggested on Sunday that he might back out of the September 10 debate because ABC News would favor his opponent by giving her the questions in advance. Tensions rose on Tuesday as the two candidates' campaigns argued over whether candidates should have their microphones muted when their opponent is speaking.