Prince William criticized the illegal wildlife trade while speaking at a World Bank conference in Washington, D.C., on Monday, calling it "one of the most insidious" forms of corruption in the world.

"Wildlife crime goes to the heart of our security. It recognizes neither national borders nor national interests. It distorts economic development, undermines the rule of law, and fuels sources of conflict,” William said. "Unchecked, it could be a factor in the spread of infectious diseases with a devastating toll.”

The prince made his remarks a day ahead of the UN's Anti-Corruption Day. 

Earlier, William met with U.S. President Barack Obama in the Oval Office and was given a tour of the White House. The visit marks the prince's first trip to Washington.

Meanwhile, on her first day in New York, Kate wasn't taking in tourist sites like the Empire State Building or Times Square, but instead focused on one of her passions — helping disadvantaged youth. 

William-Kate-Beyonce-Jay-Z

Britain's Prince William, second from right, talks with rapper and entrepreneur Jay-Z , far right, as Kate, left, the Duchess of Cambridge, chats with Jay Z's wife, entertainer Beyonce, during Monday's NBA game at Barclays Center. (Kathy Willens/The Associated Press)

Kate spent part of the day wrapping presents with students at the Northside Center in Harlem. The centre offers support and care for children working to overcome issues such as poverty, discrimination and mental health. 

Royalty meets celebrity

While the younger children, aged four and five, don't know what a duchess is, they did know one was coming and were excited, according to Thelma Dye, executive director of the centre.

"When they look back on this, when they're much older, it'll be very meaningful to them in terms of 'wow, they understood, they cared, the world cares,'" she said prior to the visit.

Royals US Visit

Kate accepts flowers from a student outside the Northside Center for Child Development on Monday in New York. (John Minchillo/Associated Press)

William was to return to New York to attend an evening reception co-hosted by Hillary Clinton to highlight his conservation work.

The busy couple reunited later to see the Brooklyn Nets take on LeBron James and the Cleveland Cavaliers at Barclay Center. While courtside, they met hip hop's royal couple, Beyoncé and Jay-Z, who previously owned a stake in the Nets before giving it up last year.

On Tuesday Will and Kate are scheduled to tour the National September 11 Memorial Museum. The trip ends with a star-studded gala at the Metropolitan Museum of Art at a fundraiser hosted by Tom Hanks. The money raised will go to the royal couple's alma mater, St. Andrews University, where the two first met.

Kate and William's three-day visit to the U.S. is their first official tour since a 2011 trip to California.

Can't see on mobile? View LeBron James's Instagram with Will and Kate.

With files from The Associated Press