The UK's Prince William and his wife Kate arrived in the US city of Boston on Wednesday before the awards ceremony for the Earthshot Prize.
Crowds waited in torrential rain to catch a glimpse of the couple and to welcome them to City Hall in Boston, the home town of president John F Kennedy.
It was the late president who inspired the prince to launch Earthshot, based on Kennedy’s moonshot challenge – to put a man on the Moon.
“Like President Kennedy, Catherine and I firmly believe that we all have it in ourselves to achieve great things, and that human beings have the ability to lead, innovate and problem-solve," Prince William told the crowd.
“We cannot wait to celebrate the Earthshot Prize finalists later on this week, and we are both looking forward to spending the next few days learning about the innovative ways the people of Massachusetts are tackling climate change.”
Most of the trip will be focused on the Prince of Wales's initiative to find and fund the environmental entrepreneurs of a new generation through the Earthshot awards, which support companies and people focused on helping the planet.
The royal couple's visit coincides with a trip being made by US President Joe Biden, who will reportedly be making an appearance at a Democratic fundraiser in the city.
"The President intends to greet the Prince and Princess of Wales when he is in Boston," White House Press Secretary Karine Jean-Pierre said on Wednesday.
Notable members of the Kennedy family - in pictures
"We are still finalising and working through the details."
In their first trip abroad since the death of Queen Elizabeth II, the couple's visit started with a meeting with Boston Mayor Michelle Wu at city hall.
The couple will on Thursday visit Greentown Labs, a climate technology start-up incubator in Somerville, to learn about local innovations.
They will then head to Chelsea to visit Roca, a non-profit organisation focused on reducing youth violence, local news station WBUR reported.
On Friday, their last day in Boston, they will visit Harvard’s Centre of the Developing Child in Cambridge before taking a tour of the John F Kennedy Library with Caroline Kennedy, member of the famed political family and US ambassador to Australia.
Later that same day, they will reveal the five winners of the Earthshot awards at MGM Music Hall in Fenway.
Earthshot offers £1 million ($1.2 million) in prize money to the winners of five separate categories: nature protection; clean air; ocean revival; waste elimination; and climate change.
The winners and all 15 finalists also receive help in expanding their projects to meet global demand.
The initiative, which has a total prize fund of £50 million, was launched in 2021 and will continue every year until 2030, with people from around the world presenting ambitious projects to fix the globe's biggest environmental problems.
Earthshot awards 2022 lineup — in pictures
After their arrival at Boston's Logan International Airport, the Prince of Wales expressed his appreciation for the city's hospitality on Twitter.
"Catherine and I are delighted to be back in the United States," Prince William wrote.
"On this, our first overseas visit since the death of my grandmother, I would like to thank the people of Massachusetts and particularly of Boston for their many tributes paid to the late queen.
"Catherine and I can't wait to meet many of you in the days ahead."
The BBC’s Clara Amfo and American actor Daniel Dae Kim are co-hosting the event, and actors Rami Malek, Catherine O’Hara and Shailene Woodley are presenting awards.
Billie Eilish and Ellie Goulding are performing.
The ceremony will be broadcast by the BBC in the UK, PBS in the US and Multichoice across Africa.