The first UN youth climate summit kicks off in New York City on Saturday with a panel of speakers that includes 16-year-old Swedish environmental activist Greta Thunberg.

She was on Capitol Hill on Wednesday, wrapping up a six-day visit to Washington, appearing with other young activists before the House foreign affairs subcommittee on climate change.

She urged politicians to “just tell them the truth,” when asked how children can get more involved in learning about climate change and doing something about it.

On Friday, Thunberg joined a rally in New York, where it’s estimated about 100,000 people marched, many of them teens who followed the call for a climate strike. Thunberg started the climate strike movement last year, calling for weekly demonstrations.

Hundreds of thousands of young people marched in cities around the world on Friday to demand that politicians heading to Monday’s UN summit on climate change take immediate action to combat climate change.

In an interview published by The Associated Press on Saturday, Thunberg was asked for her impression about the political situation in the United States around climate change.

Founder of Fridays For Future Greta Thunberg speaks to a congressional hearing on Capitol Hill on Friday. The teen recently sailed across the Atlantic Ocean in a zero-carbon emissions sailboat to travel to New York, which is hosting the UN Climate Action Summit on Monday. (Alex Wong/Getty Images)

“It’s a bit worse than in other countries,” she said. “The arguments for continuing to not do anything and the empty words and promises and lies are the same. Some countries are more extreme than others but it’s not much different.”

She said nothing may come from the upcoming summit, but added that “giving up cannot be an option.”

The UN has called climate change the “defining issue of our time.” Scientists have warned that global warming will subject Earth to rising seas, as well as more heat waves, droughts, storms and flooding.