Swedish environment activist Greta Thunberg speaks at a climate protest outside the White House in Washington.

Greta Thunberg, the 16-year-old Swedish climate activist, addressed a gathering here outside the White Hose and said that the movement will not relent in its demands for action.

"I just want to say I'm so incredibly grateful for every single one of you, I'm so proud of you, who have come here, and I - it's a lot of people. This is overwhelming," she told the gathering of some 200 young people on Friday.

"Just never give up, we will continue and see you next week," Thunberg said, referring to the Global Climate Strike planned for September 20, Efe news reported.

Swedish youth climate activist Greta Thunberg, center, marches with other young climate activists.

In August 2018, Thunberg, then 15, began skipping school on Fridays to demonstrate outside Sweden's Parliament. Her example has been emulated by thousands of students worldwide, giving rise to the Fridays for Future movement.

The Washington chapter of the movement protest weekly near the White House, but Thunberg's presence made Friday's mobilization a media event.

Among those who spoke on Friday was Jonah Gottlieb, 17, the executive director of the National Children's Campaign, who said that the aim of the protests was to "send a message" to the people in power.

"They know that we're coming after them," he said. "This is our planet and we are here to stay."

GretaThunberg attends a climate protest outside the White House.

The crowd also heard from Nadia Nazar, the 16-year-old founder of the group Zero Hour.

"We're striking today to save tomorrow, not to save life in 50 years but to save tomorrow," she said.

Thunberg travelled to the US to address the September 23 UN Climate Action Summit.

She refuses to fly because of the emissions associated with air travel and when the UN invited her to the summit, she faced the challenge of getting to New York without flying.

Indo-Asian News Service