Britain's Prince William and his wife Kate were to crown their whirlwind tour of New York on Tuesday with a gala dinner to honor the university where they fell in love.

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.

The 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.

Their three-day visit -- their first to America's biggest city -- is a mix of diplomacy, supporting their favorite causes and promoting British business.

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.

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.

The names of every person who died are inscribed into bronze panels that border the pools and built in the footprint of the Twin Towers.

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.

Hollywood salute

The couple toured the museum, built into the bedrock of the Twin Towers and which documents the 2001 attacks and their legacy.

They spent time looking at some of the devastating wreckage that stands testament to the horror of the attacks and at the photographs of victims.

After the museum, they were whisked away to a youth organization that fosters artistic and intellectual development in Manhattan's upmarket Soho district to watch an arts performance.

They then mingled with the likes of British actor Patrick Stewart and Hollywood producer Harvey Weinstein at a reception to celebrate creative British talent.

For the occasion, Kate wore a high-necked black maternity dress styled with a gold necklace and drop earrings.

Later in the afternoon, William went up The Empire State Building, while his wife rested. The couple, who are in the United States without their baby son George, are expected to fly home after the dinner.

King James

New Yorkers have welcomed the British couple with warmth and hospitality -- but also some amusement and bewilderment.

On Monday, LeBron James enthralled them with a brilliant display as he led the Cleveland Cavaliers to victory over the Brooklyn Nets at the Barclays Center.

The four-time NBA Most Valuable Player and double Olympic gold medalist -- known as "King James" -- gave the couple a Cavaliers shirt marked Cambridge and another for the one-year-old Prince George.

"This very moment will be forever remembered and put up in my house. It's all good and all smiles on this side," James wrote on his Instagram page next to a photo with the royal couple.

James caused consternation amongst British royal-watchers however, breaching protocol by putting a friendly arm around Kate in a post-match photo.

Jay-Z and Beyonce, who sat opposite them on the other side of the court during the game, chatted with the couple to deafening cheers from the crowd.

The couple have stayed at the Carlyle Hotel, where William's mother Diana used to stay.

Their visit has drawn comparisons with the 1985 visit made by Charles and Diana, when the princess dazzled Americans by dancing with US president Ronald Reagan and Hollywood star John Travolta.