Prince William and his pregnant wife Kate head to New York on Sunday for a glitzy visit that marks a step-up in their role representing Britain abroad, royal commentators said.
Photo taken on July 2, 2014 to mark the first birthday of Britain's Prince George shows Prince William (R) and Kate, Duchess of Cambridge with George during a visit to the Natural History Museum in London
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 -- who will not be on the visit -- 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.
- Obama meeting a coup -
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."
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.
It will be the first time either William or Kate will have been to New York or Washington.
The couple will attend their first NBA basketball game on Monday, the league said, when they will see LeBron James and his Cleveland Cavaliers visit the Brooklyn Nets.
Sir Peter Westmacott, British ambassador to the US, told CBS News that he was confident the protests that have taken place over several nights in New York demanding justice for black men killed by white policemen would not overshadow the visit.
"We obviously hope not because this is a visit to which we attach a great deal of importance," he said.
- Asia on horizon -
William, who is training to become an air ambulance pilot in his day job, is also preparing for a trip to Japan and China in late February-early March, without Kate, who is due to give birth in April.
That visit is being viewed in Britain as an attempt to improve top-level diplomatic relations with Beijing.
"In terms of foreign travel, I would guess that he and his younger brother Prince Harry would be the ones that do it in future because they have got huge appeal," Junor said.
"He's definitely a draw, people love him the world over. They will use him, for sure," said the author, who wrote "Prince William: Born to Be King".