Prince William has met US President Barack Obama at the White House as part of a three-day visit.
The Prince held talks with President Obama in the Oval Office, in advance of delivering a speech to the World Bank on wildlife crime.
During the speech, he described the illegal wildlife trade as “one of the most insidious forms of corruption and criminality in the world today”.
His wife, the Duchess of Cambridge, visited a New York children’s centre.
The couple arrived in New York on Sunday night, with the prince travelling to Washington alone on Monday.
At the White House, the prince joked with Mr Obama about the birth of Prince George, saying: “The excitement of the event and everything else was just chaos.”
He added that he expects a “busy year” in 2015, when Catherine is due to give birth to the royal couple’s second child.
President Obama said the prince’s work to protect endangered wildlife was “very important”.
BBC royal correspondent Nicholas Witchell said the prince had enjoyed access “most politicians can only dream about”.