WASHINGTON (REUTERS) - Swedish teenage climate change activist Greta Thunberg joined other youth leaders to urge US lawmakers to support "transformative climate action" during two days of meetings and speeches on Capitol Hill, starting on Tuesday (Sept 17).

The events are intended to drum up support ahead of a global "climate strike" on Friday in which students and workers around the world will walk out to demand more action to fight global warming and pressure leaders attending the annual United Nations summit in New York later this month.

Democratic Senator Ed Markey, chair of the Senate Climate Change Task Force, hosted a news conference kicking off the meetings with the activists on Tuesday morning, before including them at the task force's weekly meeting to discuss their"intergenerational" effort to combat climate change.

"This movement is something that comes at a critical time,"Markey said outside the Capitol building. "The science has made it very clear that the planet is running out of time."

Thunberg had no plans to speak at Tuesday's events, a spokesperson said.

Thunberg shot to international fame last year when she started skipping school every Friday to demonstrate outside Sweden's parliament for action on climate change.

She was nominated for a Nobel Peace Prize this year after the number of students joining her strikes - dubbed "Fridays for Future" - broke two million across 135 countries.

In the United States, organisers of the planned Sept 20 strike have put forward a list of eight demands on elected officials, including enacting a Green New Deal - an effort to transform the US economy in a decade by shifting to 100 per cent renewable energy.

Markey is a co-sponsor of the Green New Deal congressional resolution with Representative Alexandria Ocasio-Cortez, a high-profile New York Democrat who plans to meet with the activists this week.

Republican lawmakers and Trump administration officials have pilloried the Green New Deal as fantasy. Trump is among a small minority of global leaders who have openly questioned the science of climate change. He has announced his intention to withdraw the United States from the Paris Climate Agreement, a global pact to stem the rise in global temperatures that he says would be damaging to the US economy.

Nadia Nazar, co-founder the Zero Hour advocacy group and a youth activist speaker, said Friday's global strike would usher in "the beginning of the Green New Deal."

"The generation of the Green New Deal will not only survive but we will thrive. We will no longer be known as the kids fighting the apocalypse. We will be known as the solution to the climate crisis," she said.