WASHINGTON  - Environmental activists have hailed the first moves by U.S. President Barack Obama to reduce the country's greenhouse gas emissions by setting tough new fuel efficiency and pollution standards for the country's cars and trucks, steps that his predecessor, George W. Bush, had rejected or ignored.

In a mid-morning White House appearance six days into his new job, Obama directed the Environmental Protection Agency (EPA) to reconsider the Bush administration's denial of a 2007 request by California and 13 other states to implement strict new limits on tailpipe emissions that contribute to global warming.

U.S. President Barack Obama signs executive orders on combating climate change during a ceremony in the East Room of the White House in Washington, January 26, 2009. Watching on is Transportation Secretary Ray LaHood (C) and EPA Administrator Lisa Jackson.(Jason Reed/Reuters) He also directed the Department of Transportation to follow through on Congressional legislation to raise existing fuel economy standards on new cars and lorries by 40 percent beginning in 2011.

Both directives, once the administrative process required to implement them is completed, are sure to have a major impact on the reeling U.S. automobile industry which, along with the major U.S. oil companies, has long resisted the imposition of major new fuel efficiency and pollution standards.

"For eight years, President Bush blocked the country's progress on global warming solutions," said Steven Beil, Greenpeace's Global Warming Campaign Director. "At long last, the era of obstruction and denial is over. President Obama's directives recognise that America is ready to tackle global warming."

Obama's announcement coincided with the appointment by Secretary of State Hillary Clinton of a special envoy on climate change, Todd Stern, a senior White House aide under President Bill Clinton and his top negotiator at international talks that culminated in the 1997 Kyoto Protocol, the international agreement that required wealthy countries to reduce their greenhouse emissions below 1990 levels by 2012.

While President Clinton signed the Protocol, he never submitted it to the Senate for ratification, and, shortly after taking office, Bush rejected the agreement on the grounds that its implementation would harm the U.S. economy.

"The time for denial, delay and dispute is over," Stern said at a brief State Department ceremony Monday. "The time for the United States to take up its rightful place at the negotiating table is here...We will need to engage in vigorous, dramatic diplomacy."

Obama's directives were the latest in a series of actions taken since his inauguration Jan. 20 - among them, closing the Guantanamo detention facility within one year; banning coercive interrogation techniques on detainees; and lifting an eight-year by on U.S. funding of overseas clinics and other organisations that support or perform abortions. The swift moves were designed both to fulfill campaign promises and dramatise the difference between the Bush administration and his own.

"This is a clean break from the previous administration's do-nothing approaches on global warming and U.S. oil dependence," said Kevin Knobloch, president of the Union of Concerned Scientists (UCS) about Monday's announcements.

He said the decision to permit states to set stricter emission standards was a "clear indication that the new administration is ready to lead on energy and global warming," and added, "With this announcement, President Obama is beginning to make good on his campaign pledge to restore science to its rightful place in federal policy-making."

In his announcement, Obama stressed that both moves were aimed at reducing U.S. dependence on oil, which he called "one of the most serious threats that our nation has faced. It bankrolls dictators, pays for nuclear proliferation and funds both sides of our struggle against terrorism," he said.

And he described the "long-term threat of climate change" in words that the Bush White House reserved only for its "global war on terrorism".

"(I)f left unchecked, (climate change) could result in violent conflict, terrible storms, shrinking coastlines and irreversible catastrophe," warned Obama who, since his inaugural address, has appeared determined to underline the gravity of the many challenges facing the country and the necessity of confronting them.

"Year after year, decade after decade, we've chosen delay over decisive action. Rigid ideology has overruled sound science. Special interests have overshadowed common sense," he said. "Now America has arrived at a crossroads."

The two directives issued Monday, in addition to his proposed economic stimulus plan that includes billions of dollars for clean energy programmes, should constitute "the first steps in our journey toward energy independence."

The first directive requires the Transportation Department, which is headed by a former Republican congressman, Roy LaHood, to proceed with implementing legislation passed by Congress in 2007 - but ignored by Bush - requiring U.S. automobile manufacturers to meet a 35-miles-per-gallon (56 kms) fuel-economy standard, a 40-percent increase over current standards.

Congress originally approved a 2020 deadline for the higher standard, but Obama said he wanted to move that back to 2011. If all automobiles complied with the proposed standard, more than two million barrels of oil a day, or "nearly the entire amount of oil that we import from the Persian Gulf," could be saved, Obama said.

The second measure ordered EPA Administrator Lisa Jackson to review a request from California and 13 other states to set automobile emissions standards stricter than those required by the federal government.

California Gov. Arnold Schwarzenegger had asked the Bush administration for the first time in 2007 to "waive" the application of federal law so that his state could impose the tougher standards to help it comply with Kyoto's requirements, but Bush, backed by the auto and oil industries, refused to grant it. Schwarzenegger last week asked Obama to review his predecessor's decision.

"(T)he federal government must work with, not against, states to reduce greenhouse gas emissions," Obama said Monday with the EPA's Jackson at his side. "California has shown bold and bipartisan leadership through its effort to forge 21st-century standards, and over a dozen states have followed its lead. But instead of serving as a partner, Washington stood in their way."

"The days of Washington dragging its heels are over," he added. "My administration will not deny facts; we will be guided by them."

"We believe that the auto industry should have no trouble meeting the challenge set by our new president," said Ann Mesnikoff, Washington director of the Sierra Club. "It has the technology and the know-how to comply with both California's standards and new fuel economy standards. It is time for the industry to demonstrate to the American people (who have already given them billions in taxpayer dollars) that they are committed to meeting the standards that science and the President have stated are necessary."

Indeed, the Auto Alliance, the industry's lobby group, said in a statement that it "supports a nationwide programme that bridges state and federal concerns and moves all stakeholders forward, and we are ready to work with the administration on developing a national approach."