Dr John Holdren says the last eight years have been "wasted" in tackling CO2 emissions
The US is moving toward leading the climate change debate, rather than lagging behind, according to President Obama's chief scientific advisor.
In his first international interview since taking the post, Dr John Holdren told the BBC that he wanted to take the politics out of scientific advice.
He also revealed that Nasa's plans to send an American back to the Moon by 2020 could be delayed.
It was important now, he said, to balance science spending priorities.
Dr Holdren's previous job was professor of environmental policy at Harvard University.
His appointment as President Obama's chief scientific advisor was a clear signal that, unlike his predecessor, the new President would embrace rather than dismiss the scientific evidence that the burning of fossil fuels was warming the planet and dangerously destabilising its climate.
Dr Holdren told BBC News that the new administration was making progress in persuading the American public and Congress that cutting carbon dioxide emissions was in the national interest.
He said he hoped to convince both the public and US policy-makers in time for the next round of negotiations for a new international carbon reduction treaty in Copenhagen in December.
"It would be advantageous for the United States to go to Copenhagen as a leader," he said.
During the Bush Administration, critics say, politics interfered with science
"We should demonstrate that we are a country that has embraced a mandatory, economy-wide approach to reducing greenhouse gas emissions.
"I think we are on our way to becoming leaders, and it's about time."
The United States House of Representatives recently passed the Waxman-Markey Bill, setting an emissions reduction target and introducing a cap and trade scheme.
Dr Holdren was confident that that a similar bill would be passed by the US Senate in time for the Copenhagen summit meeting.
But he said that the US would not be in a position to meet the European Union demands to set a carbon reduction target of between 25 and 40% by 2020.
"I don't think the European Union's preferred number is achievable for the United States at this point," he said.
"If we hadn't wasted the past eight years then we probably could have achieved that target. But we did waste the last eight years and, as a consequence, it doesn't make a bit of sense for us to embrace a target that is not realistically within our reach".
In his inauguration speech, President Obama pledged to ensure that facts and evidence were never twisted or obscured by politics or ideology, as some scientists have alleged occurred, during the Bush Administration, on environmental issues.
Next week Dr Holdren will set out new regulations that he says will prevent scientific advice from being influenced by politics.
"We are not going to have public relations minders changing the testimonies of federal agencies on a basis that is (not) scientific.
"Unfortunately, under the last administration that was not the case."
Dr Holdren also said that pressing demands on public finances had made it important to review Nasa's plans to send an American to the Moon by 2020.
"The previous administration articulated a grand vision to go to the Moon, Mars and beyond, but they never produced a budget for achieving that vision.
"We live in a resource constrained world and we have to understand what our options are now," he said.
The results of a White House review by former Lockheed Martin CEO Norm Augustine on the lunar exploration plans are due out by the end of August.
But Dr Holdren told BBC News that the review may well conclude that the proposed mission should be delayed, because it would mean that resources would have to be diverted away from essential environmental monitoring projects.
"To focus all our resources to get to the Moon in a particular year - or to get to Mars by a particular year - would impair our ability to understand what's happening on our planet," he said.
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