Meghan, the Duchess of Sussex, called on young girls to make their voices louder than ever as they push the world in a "more inclusive, more just, and more empathetic direction."

"The moment we are living through right now asks all of us to do more," Meghan said Tuesday in a speech at the 2020 Girl Up Leadership Summit. "It's a moment where your voices, and your action, have never been more urgently needed."

"Believing in true equality is not enough -- it's going to take more than belief, we have to work for it every day; even when it's hard and even when it makes others feel uneasy," said Meghan. "We have to speak up for ourselves and we have to speak out for others who struggle to be heard."

Meghan delivered her remarks virtually to more than 40,000 of the summit's attendees, girls ages 13 to 22 who live across 172 countries. Girl Up is a leadership program for young girls that is a campaign of the United Nations (UN) Foundation.

VIDEO: Duchess Meghan speaks to young women at Girl Up leadership summit
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Meghan shares a powerful message on using your voice: "We have to speak up for ourselves."

"I want to share something with you. It's that those in the halls and corridors and places of power -- from lawmakers and world leaders to executives -- all of those people, they depend on you more than you will ever depend on them. And here's the thing: they know this," Meghan told the young women. "They know that all of you, at a younger age than any modern comparison, are setting the tone for an equitable humanity. Not figuratively, literally."

"This is a humanity that desperately needs you. To push it, to push us, forcefully in a more inclusive, more just, and more empathetic direction," she said. "To not only frame the debate, but be in charge of the debate -- on racial justice, gender, climate change, mental health and wellbeing, on civic engagement, on public service, on so much more. That's the work you're already out there doing."

Meghan joined the likes of former first ladies Michelle Obama and Hillary Clinton and her friend and fellow actress Priyanka Chopra as a speaker at this year's summit.

"Continue to believe in yourselves, believe in what makes you unique, and don’t be afraid to do what you know is right even when it’s not popular...even when it’s never been done before...even if it scares people," Meghan said Monday. "And even if it scares you."

The duchess -- who has faced online bullying and intense media coverage since marrying Prince Harry two years ago -- also spoke to the young women about how they can be positive forces in today's digital world.

"Your generation is often referred to as digital natives, and you understand that our online world has the power to affirm and support as much as it does to harm," she said. "We are not meant to be breaking each other down; we are meant to be building each other up."

"So use your voices both on-and-offline to do just that -- build each other up, support each other," Meghan added. "There will always be negative voices and sometimes those voices can appear to be outsized, and sometimes they can appear to be painfully loud. You can and will use your own voices to drown out that noise. Because that's what it is. It is just noise. But your voices are those of truth and hope and your voices can and should be much louder."

"You have, rooted in your convictions, the ability to craft a world that you know is just and kind and your gut will tell you what's right and what's wrong; what's fair and unfair. The hardest part -- and it was the hardest part for me -- is to chase your convictions with action," she said.

Meghan ended her remarks by telling the young women, "I will be cheering you on, so will my husband, so will Archie, as you continue marching, advocating, and leading the way forward."

The speech marked one of the few times Meghan has spoken publicly since moving with Prince Harry to Los Angeles earlier this year and transitioning to a non-working member of the royal family.

Harry and Meghan signed on last month as speakers with The Harry Walker Agency, the global speaker's bureau that represents a range of celebrities and power brokers from former Presidents Bill Clinton and Barack Obama to Michelle Obama and football star Tom Brady.

The couple also plans to launch a nonprofit venture named Archewell, but no further details have been announced.