Prince William and his pregnant wife Kate head to New York today for a glitzy visit that marks a step up in their role representing Britain abroad, royal commentators said.
The three-day trip will see the Duke and Duchess of Cambridge, both 32, mix diplomacy with supporting their favourite causes and promoting British business interests.
Crucially for William, he will meet US President Barack Obama in the White House on Monday for talks about illegal wildlife trading, an issue close to the prince's heart.
William, second in line to the throne after his father Prince Charles, is starting to do more of the long-haul work for the British monarchy as Queen Elizabeth II approaches her nineties.
"It's a significant trip which is trying to establish William further in a diplomatic, statesmanlike role," Robert Jobson, author of "The New Royal Family" on William, Kate and their baby son Prince George, told AFP.
The official visit will be only the second undertaken by William and Kate outside the Commonwealth family of nations, following a brief stop in California at the end of their 2011 Canada tour.
And rather than visiting on behalf of Queen Elizabeth or touring one of her realms, this time they will be expressly visiting on behalf of the British government.
The visit will undoubtedly revive memories of the 1985 trip made by William's parents, Charles and Diana, when the princess, wearing a dazzling gown, danced with US president Ronald Reagan and Hollywood star John Travolta.
Jobson said palace officials were keen to balance the spotlight better than they did with Charles and Diana.
"They don't simply want it to be dominated by the Kate factor," he said.
"They're trying to keep William and Kate's programme designed carefully so that she doesn't upstage him everywhere he goes, because British and other media seem to be obsessed with what Kate wears and the baby bump," Jobson said.
"They've obviously got a more serious agenda, which is that this is the future king meeting the president of the United States and entering the special relationship," he added.
After the meeting with Obama, William will address the World Bank on illegal wildlife trading.
"It is quite a coup for William that he has been invited to the White House by Obama because this is his topic, something he has specifically raised awareness about," royal biographer Penny Junor said.
