The couple will start their final day of their New York City tour speaking with Mr Guterres before attending climate change concert Global Citizen Live this evening.
With performances from Ed Sheeran, Sir Elton John, Kylie Minogue, Metallica and Coldplay the event aims to pressure world leaders to adopt vaccine equity policy to help end the Covid-19 pandemic.
On Friday Meghan and Harry visited Harlem’s PS 123 Mahalia Jackson school where overwhelmed children were pictured embracing the couple.
They were joined New York City mayor Bill de Blasio and Governor of New York State Kathy Hochul at the skyscraper’s observatory.
The couple posed for photographs at the top of the skyscraper against a panoramic backdrop.
Mr de Blasio’s wife, the first lady of New York, writer and activist Chirlane McCray, and their son Dante de Blasio also joined the group.
Asked by a reporter if they were enjoying their trip to New York, Meghan, dressed in a black high-necked coat and black trousers, smiled and replied: “It’s wonderful to be back, thank you.”
The visit is the couple’s first public appearance together since the birth of their daughter Lilibet in June.
One World Trade Centre has been built on the site of the original twin towers.
Their visit comes just two weeks after the 20th anniversary of the September 11 attacks.
Prince Harry and Meghan remembered the anniversary and transformed their website Archwell to mark the milestone.
Archewell’s homepage had a black drop with the words “In Memoriam, September 11, 2001” at the top.