President Barack Obama meets with Britain's Prince William in the Oval Office of the White House in Washington, Monday, Dec. 8, 2014. (AP Photo/Jacquelyn Martin)

NEW YORK, N.Y. - Britain's Prince William sat down with President Barack Obama in Washington on Monday and unveiled an effort to curtail illegal wildlife trading, while his wife, Kate, made an impression of a down-to-earth duchess on preschoolers and prominent British expats in New York.

In the first full — very full — day of the popular royal couple's first visit to either place, William went to the White House and spoke at a World Bank conference. Kate wrapped Christmas gifts and helped children decorate picture frames while touring a child development centre with New York City's first lady, then talked technology, theatre and more with a British-success-story guest list at a lunch at the consul general's home.

The Duke and Duchess of Cambridge are on their first official trip to the U.S. since 2011. William, speaking at the World Bank, announced a new task force to develop recommendations within a year on how the transportation industry can help stop wildlife trafficking, calling it "one of the most insidious forms of corruption and criminality."

Meanwhile, the duchess and city first lady Chirlane McCray met with families and heard about the work of the Northside Center for Child Development, which offers mental health and educational services.

"Very nice to meet you," Kate told a classroom of 3- and 4-year-olds, who were embellishing picture frames with stickers.

After encouraging a boy named Sammy in his work, the duchess, who is expecting the couple's second child, turned to a girl named April.

"Where should I put this one?" Kate asked, affixing a sticker.

Kate and McCray later wrapped children's Christmas presents in the centre's gymnasium, with Kate joking that she hoped she'd be given a square package to tackle.

Later, Kate chatted with lunch guests including actor Matthew Rhys, TV and theatre producer Colin Callender, Parsons The New School of Design fashion dean Simon Collins and tech news site Mashable founder Pete Cashmore. She asked how Callender's recent New York staging of "Macbeth" had been received and told Cashmore his "must be such an exciting industry to be a part of."

The royals also attended an early evening reception highlighting wildlife conservation efforts with former U.S. first lady Hillary Rodham Clinton and her daughter, Chelsea Clinton.

During the event at the British consul general's residence, William made a brief speech on the plight of the world's most iconic species being "butchered in the name of trinkets and medicine" before ending it on a lighter note.

"I'm off to shoot some hoops now, or whatever it is you Americans say." The couple then travelled to the Barclays Center in Brooklyn to catch an NBA game.

The royals are visiting a city where thousands of people have protested over the past week to decry a grand jury's decision not to indict a white police officer in the chokehold death of an unarmed black man, Eric Garner. More than 200 people demonstrated outside the Barclays Center while the royals took in the game.

During pre-game warmups, Cavaliers star LeBron James wore a T-shirt saying "I can't breathe," a rallying cry that has developed around Garner's last words. He was joined by Cavaliers player Kyrie Irving and several Brooklyn Nets players.

Earlier, James had said that playing with William and Kate in the audience would be "a huge honour."

As the royal couple headed to their seats during the third quarter, fans stood and cheered. The royals were shown on the overhead scoreboard during a stoppage of play. Kate, wearing a grey jacket, waved to the camera as the crowd roared. Jay-Z and Beyonce were led across the court between the third and fourth quarters to chat with them.

The royals' schedule for their three-day trip includes a visit to the National Sept. 11 Memorial and Museum, a visit to showcase arts education at a youth organization, and a black-tie fundraiser for their alma mater, the University of St. Andrews.

Earlier Monday, Kate, dressed in a black coat by the British fashion brand Goat, was greeted with cheers from several dozen spectators as she arrived at the Northside Center. Aaron Victor and wife Crystal Pizarro had waited almost an hour on a freezing day with their 3-year-old daughter, London, to catch a glimpse of the duchess.

"It was a very good experience, and I'm glad she got to see her," Pizarro said.

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Associated Press writer Julie Pace and Business Writer Tomoko A. Hosaka contributed to this report from Washington.

News from © The Associated Press, 2014