Prince Harry and Meghan Markle arrive in New York and visit One World Observatory

Prince Harry and Meghan Markle smiled and waved to waiting fans and photographers as they arrived at New York's One World Trade Centre on Thursday.

The Duke and Duchess of Sussex popped on their face masks at the door before heading up to the building's observatory on the top floor where they posed for photographs with Harry looking dotingly at his wife in one sweet snap.

The visit kicks off the couple's US East Coast trip, which will also include appearing during the Global Citizen Live event over the weekend.

For her first official post-baby appearance since her daughter's birth, Meghan donned a dark navy wide-legged trouser with a turtleneck knit tucked in.

The mum-of-two added a long-length navy coat and accessorised with pointed-toe heels.

RELATED: Prince Harry and Meghan Markle 'planning trip to the UK before Christmas'

The 40-year-old has only made one appearance - in a video released on her birthday - since welcoming daughter Lilibet in June.

And the couple also featured in new photos on the cover of TIME Magazine, after being named among their 100 Most Influential People in the World last week.

The Duchess styled her brunette locks in her go-to low bun with a centre part and slicked back the usual tendrils that frame her face.

Prince Harry matched his wife in a sharp navy suit and tie.

During their visit to the observatory, they were joined by New York Governor Kathy Hochul and NYC Mayor Bill De Blasio, who was accompanied by wife Chirlane McCray and their son Dante de Blasio.

Meghan, who is a huge advocate for empowering women and women's rights must have had an especially happy moment meeting Governor Hochul, who is New York's first female governor and came into office last month.

The visit must be especially poignant for Prince Harry too, who has previously served in Afghanistan after the September 11 attacks — with the building on the site of the former World Trade Centre.

While not an official royal tour, the couple are expected to undertake a handful of engagements before appearing at New York's Central Park during the Global Citizen Live event on Saturday, to push for global vaccine equity.

The 24-hour livestream event will include Aussies Hugh Jackman and Keith Urban, as well as Lorde, Ed Sheeran, The Weeknd, Adam Lambert, Black Eyed Peas, Green Day and Coldplay.

Multiple events are being held across the world, in cities including Lagos, Paris, New York City, London, Sydney, Seoul, Rio de Janeiro and Los Angeles.