Thunberg was praised as a "superpower" for her work, with one senator describing the 16-year-old and other young activists as bringing "moral clarity" to the fight against global warming.

But she has rejected the accolade, telling Tuesday's Senate forum, "save your praise".

"We don't want it," she added, especially if officials intend to talk about climate change "without doing anything about it."

Thunberg gained international attention by inspiring a series of protests and school strikes, including one set for Friday.

Activists are calling for immediate action from the world's governments to halt global warming, reduce fossil fuel consumption and avert environmental catastrophe.

"I know you're trying," she told Democratic senators at an invitation-only forum, "but just not hard enough. Sorry."

Instead of listening to her and other teenagers, lawmakers should invite scientists for their expertise on ways to slow a catastrophic rise in global temperatures, Thunberg said.

"This is not about us. This is not about youth activists," she said.

"We don't want to be heard. We want the science to be heard."

Despite her request, lawmakers bombarded Thunberg and other youth activists with praise, saying they had a sparked a global movement that is already being felt in the 2020 presidential campaign and in the halls of Congress, where lawmakers are debating proposals such as the Green New Deal.

The Green New Deal would shift the US economy away from fossil fuels such as oil and coal and replace them with renewable sources such as wind and solar power.

Last month, Thunberg crossed the Atlantic Ocean in a solar-powered boat, landing in New York City on August 28.

She's in Washington for several days of rallies and lobbying efforts in advance of Friday's global climate strike and will address the UN Climate Action Summit in New York on Monday.

Australian Associated Press