U.S. President Donald Trump has offered to mediate a long-running dispute between Egypt and Ethiopia over the latter’s construction of a giant dam on the Nile. According to the experts, Trump attempted to broker a deal over the dam during his first term, but saw his efforts rebuffed by Ethiopia’s Prime Minister Abiy Ahmed, who felt he was siding with Egypt--a strong U.S. ally. Trump has previously claimed that the dam "substantially" lowers water volumes flowing into the Nile, echoing Egypt’s sentiments. Last year, Ahmed inaugurated…