WASHINGTON (AFP) - US President Barack Obama on Thursday will order the government to cut its own greenhouse gas emissions and use more renewable energy, the latest drive to bypass a hostile Congress.

Obama will sign an executive order to cut government emissions by 40 per cent over 2008 levels in the next decade and source 30 per cent of electricity from renewables, the White House said.

The measures could save taxpayers around $18 billion (S$25 billion), officials said.

The federal government operates an estimated 360,000 buildings and 650,000 vehicles, making it the country's largest single energy consumer.

"These goals will make sure the federal government is leading by example," said Brian Deese, a senior advisor to Obama.

Now in the autumn of his presidency, Obama has refused to be shackled by the Republican-controlled Congress, wielding executive power in a way his fiercest critics say is unconstitutional.

Any measures to tackle climate change have little chance of passing muster with Republican lawmakers, many of whom deny the earth is warming.

In a further sign that Obama is determined not to become a "lame duck" in his final two years at the White House, he has also leveraged the power of his office to get companies on board.

The White House said 14 private companies who each do more than one billion dollars a year in business with the US government will also curb their own emissions.

IBM, GE, Honeywell, HP and Northrop Grumman are among the companies expected to announce their own targets.