Tareq Abu Khdeir, speaking via a representative from the US consulate in Jerusalem who was allowed to visit him in the police station, sent a message to his parents: "I am holding up OK."
The fifteen year old, who is an American citizen and attends high school in Florida, is alleged to have been badly beaten by Israeli security forces during violent clashes in East Jerusalem on Thursday.
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The Democratic presidential candidate may also have shown his cards on his choice of running mate.
The US president also shared a post on Twitter accusing Dr Anthony Fauci of misleading the public over hydroxychloroquine.
Fears over an impending second wave of coronavirus dominates Wednesday’s front pages.