EFEAlex Segura Lozano Washington

Greta Thunberg, the 16-year-old Swedish activist who has become an icon of the struggle against the climate crisis, said here Friday 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 a crowd of some 200 young people gathered across the street from the White House.