Crowds of jubilant royal watchers cheered as Britain's Prince William and his pregnant wife Kate arrived in New York on Sunday, kicking off their first official trip to the United States.

The Duke and Duchess of Cambridge's motorcade pulled up outside the Carlyle Hotel on the Upper East Side at 5:45 pm, and the couple smiled broadly before heading into the building.

Kate, who is due to give birth to the couple's second baby in April, was wearing a purple maternity coat. Their firstborn son George is not coming on the three-day visit.

Their trip will see William and Kate, both 32, mix diplomacy with supporting their favorite causes and promoting British business interests.

William is scheduled to 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 now doing more long-haul work for the British monarchy as Queen Elizabeth II approaches her 90s.

"It's a significant trip which is trying to establish William further in a diplomatic, statesmanlike role," said Robert Jobson, author of The New Royal Family.

Rather than visiting on behalf of Queen Elizabeth or touring one of her realms, 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.

And the royal couple are staying at the same New York hotel - The Carlyle, known for hosting global power players over the years - that Diana visited.

After meeting 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.

Asia on horizon

William, who is training to become an air ambulance pilot in his day job, is preparing for a trip to Japan and China in late February-early March, without Kate, ahead of her due date.

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.