Thousands demand climate action

Demonstrators called on Mr Obama to reject the $7 billion (£4.5bn) Keystone XL pipeline from Canada to Texas, and order the Environmental Protection Agency to set carbon standards for power plants.

The event was organised by local and national environmental groups, including the Sierra Club, under umbrella group Forward on Climate.

"It's by far, by far, the biggest rally on climate in US history," activist Bill McKibben told the crowd as it assembled at the Washington Monument.

Organisers said that protesters had arrived on buses from 28 of the country's states.

Van Jones, a one-time adviser to Mr Obama on the environment, was strident in his demand for change.

"President Obama, all the good you've done will be wiped out by floods, by fires, by superstorms if you fail to act now," he told the crowd.

The rally comes after the US endured record high temperatures and lengthy droughts last year, as well as superstorm Sandy, which devastated the east coast.

Mr Obama mentioned climate change during his January inauguration speech, and in Tuesday's State of the Union address he vowed to take action "for the sake of our children and our future" if Congress failed to.

The US is the world's second largest CO2 emitter.