The banquet in the opulent surroundings of the Metropolitan Museum of Art, where Hollywood actor Tom Hanks will reportedly make a toast, celebrates the 600th anniversary of the University of St Andrews in Scotland.
Yesterday's dinner comes after the royal couple, both 32, braved pouring rain to visit the 9/11 memorial in downtown New York, leaving a bouquet and handwritten note in memory of the victims of the Al-Qaeda attacks.
It was a somber note in an otherwise lightning tour that saw them hobnob with basketball superstar LeBron James, Beyonce and Jay-Z at an NBA game after William met US President Barack Obama on a solo side-trip to Washington.
Second in line to the throne after his father Prince Charles, William is increasingly taking on more long-haul work for the British monarchy as Queen Elizabeth II approaches her nineties.
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The Duke and Duchess of Cambridge, who is five months pregnant with her second child, shielded under large black umbrellas while she delicately placed a bouquet of white lilies and roses at one of the 9/11 memorial's two reflecting pools.
The site honors the nearly 3,000 people killed in the 2001 Al-Qaeda strikes on the World Trade Center, and six people who died in a first attack on the Twin Towers in 1993.
Kate wore a double-breasted cerise wool silk coat fastened with black buttons from British luxury label Mulberry, over her customary thick black tights and a pair of classic black pumps.
She wore her hair pulled back in a sleek pony tail, and finished her look by wearing black gloves and carrying a small black clutch.
William wore a dark suit.