The Obama administration, under pressure to show concrete action in the final stretch of climate change negotiations, rolled out its plans today to require automakers to produce cleaner and more fuel-efficient cars.
In an appearance at the White House, the transportation secretary, Ray LaHood, and the Environmental Protection Agency administrator, Lisa Jackson, introduced new fuel efficiency standards that would raise the average gas mileage for new cars and trucks to an average 35.5mpg by 2016.
The measures, which were first announced last May, come barely 48 hours before the first of a series of high-level events in Washington, the United Nations and Pittsburgh which will focus on climate change, and which will test Barack Obama's ability to deliver on his promises to get America to act to reduce carbon emissions.
Obama won praise from world leaders for his promises to undo George Bush's environmental record, but there is growing scepticism abroad that Democrats will be able to overcome opposition in Congress and pass legislation that would put America on a path to cutting its carbon emissions.
Jackson told reporters the new standards would save 1.8bn barrels of oil, and were the equivalent of taking 42m cars off the road. According to government estimates, the new standards would cost up to $1,300 a car by 2016 - but those costs would pay for themselves through better gas mileage.
Obama, in a visit to a General Motors plant in Ohio, said the measures, which were first announced last May, were long overdue. "This action will give our auto companies some long overdue clairty, stability and predictability."
Environmental organisations also praised the move - noting that it was the first time the EPA had used its powers under the clean air act to try to reduce global warming. The Union of Concerned Scientists called it the biggest improvement on fuel economy and exhaust standards in 30 years - although it gave far lower estimates for fuel economies than the Obama administration.
"You have to go back to the days of disco to see a fuel economy improvement like this," said Jim Kliesch, a senior engineer in the organisation's Clean Vehicles Program. "These proposed standards will be the biggest increase in fuel economy in more than 30 years. That's good news for the environment, consumers' wallets and our nation's energy security."
However, the UCS and other groups expressed concerns at measures that could provide a loophole to car makers for meeting the new requirements. Foreign automakers who sell a limited number of cars in the US will also not be held to the standard.
The new regulations will be finalised in late March.
Today's announcement was widely seen as an effort by the Obama administration to show that it is working hard to reduce America's carbon emissions despite signs that climate change legislation could be stalling in the Senate.
Democratic leaders in the Senate have delayed taking up the climate change bill so they can focus on healthcare. That has fuelled concerns in Washington and abroad that a climate change bill could falter.
Such concerns have grown as the administration comes into the spotlight ahead of a UN climate change summit next week. The summit will be attended by nearly 100 world leaders, and America - as a major polluter - is expecting pressure from the small and developing countries that will suffer the most severe consequences of climate change to show it is taking concrete action.
With that in mind, the Obama administration has carefully coordinated a number of measures to showcase its commitment to action - even in the absence of legislation.
The EPA followed by today's roll-out by announcing that it would more rigorously monitor toxic discharges from coal plants into the water supply. The announcement comes a day after three environmental organisations threatened to sue the EPA for failing to regulate the discharge of toxic metals such as lead, selenium, cadmium and mercury from the coal plants.
The EPA said the new rules, which have been pending since 1982, would be ready by 2012.
Also today, the State Department announced that the administration had signed on to a North American initiative to phase out production of another greenhouse gas, hydroflurocarbon or HFC, which is used in refrigerators and air conditioning. HFC, unlike other coolants, does not damage the ozone layer but it does contribute to climate change.