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.

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.

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.

After the meeting with Obama, William will address the World Bank on illegal wildlife trading.

It will be the first time either William or Kate will have been to New York or Washington.

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.