US Secretary of State Condoleezza Rice has said climate change is a real problem, and world leaders should forge a new global consensus on tackling it.
At a meeting of the top 16 polluting countries, Ms Rice said the US was "a major emitter" and was not "above the international community on the issue".
She said that the "growing problem" should be resolved under UN auspices.
Critics voiced concern that the US was trying to rally support for voluntary rather than binding emission cuts.
This would dilute attempts to reach a global agreement through the UN, ahead of the expiry of the Kyoto Protocol in 2012.
"All nations should tackle climate change in the ways that they deem best"
President George W Bush, who shortly after taking office in 2001 said he would not submit the Kyoto Protocol to Congress for ratification, has opposed mandatory cuts.
He has called instead for voluntary approaches - echoed by China and India.
At the talks in Washington, Ms Rice said: "Though united by common goals and collective responsibility, all nations should tackle climate change in the ways they deem best."
She challenged leaders to reduce their dependence on fossil fuels by moving toward energy sources that would reduce global warming - but without harming their economies.
Delegates will seek agreement on global goals for "energy security and reducing greenhouse gas emissions", the White House said in a statement.
President George W Bush is expected to address the meeting on Friday.
Small practical steps
Representatives from the EU and the UN Framework Convention on Climate Change are also attending the US-sponsored meeting.
The BBC's environment analyst Roger Harrabin says Europe's political leaders do not anticipate much from these talks - most have sent junior ministers or even civil servants.
However, our correspondent says they hope that perhaps some small practical steps may emerge to help share best practice between industrial sectors and they are relieved that publicly, at last, America is saying that climate change is really a problem that needs tackling.
The top UN climate official, Yvo de Boer, said he believed the discussions could feed back into the UN process.
The UN is to hold a meeting in Indonesia in December, where representatives will consider ways to tighten a mandatory clampdown on carbon emissions after the Kyoto pact expires.
Mr de Boer said it was crucial that industrialised nations committed to an approach that went "well beyond present efforts, given their historic responsibilities and economic capabilities".
Many scientists say political action is falling behind what is needed to avert lasting damage to Earth's climate.
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