Barack Obama unveiled the most ambitious climate change plan ever put forward by a US president, saying he would not condemn future generations "to a planet that is beyond fixing".
In sweeping proposals released after four years of frustrated efforts, Obama ordered new curbs on carbon emissions from power plants and called for America to ready its defences against a changing climate.
The President also surprised environmentalists by signalling that he would reject a controversial oil pipeline if it was found to "significantly exacerbate" the problem of carbon pollution.
"I refuse to condemn your generation and future generations to a planet that is beyond fixing," Obama told students at Georgetown University in Washington. "As a president, as a father and as an American, I'm here to say we need to act."
The plan announced yesterday can be carried out by executive order and does not need Congressional approval.