Tens of thousands of protesters have gathered in Washington to urge President Barack Obama to take concrete measures to fight global warming.
Waving banners and signs with slogans like "What will be your climate legacy?" the protesters called on Obama to reject the Keystone XL pipeline that would bring oil from Canada to Texas, and order the Environmental Protection Agency (EPA) to set carbon standards for power plants.
"It's time for the country to wake up; the US has been dragging its feet too long," said Mimi Body, one of the protesters on Sunday.
The event was organised by local and national environmental groups, including the Sierra Club, under an umbrella group named Forward on Climate. The Sierra Club said that 30,000 demonstrators were at the event.
"It's a big deal because the world is watching us," said Canadian-born actress Evangeline Lilly, star of TV's Lost.
"We want to challenge President Obama to be a main actor as opposed to being a puppet of the big oil companies," Lilly told AFP. "It's about telling him his speech did not fall on deaf ears."
Organisers claim the event will be the largest climate rally in US history, and includes protesters who have arrived aboard buses from 28 states.
The president mentioned climate change during his inauguration speech in January, and in Tuesday's State of the Union he vowed to take action "for the sake of our children and our future" if Congress fails to do so.
Celebrities who have signed a petition supporting the protesters include Alec Baldwin, Susan Sarandon, Morgan Freeman, Robert Kennedy Jr and Yoko Ono.
The rally comes after the United States last year endured record high temperatures and lengthy droughts, as well as superstorm Sandy, which devastated the New York-New Jersey coastline.