Sydney - Australia's commitment to tackle global warming wavered Monday with the opposition Liberal Party's shock decision to renege on a long-standing promise to introduce a carbon-trading scheme by 2012.

Prime Minister Kevin Rudd's Labor government is committed to a 2010 deadline for setting a cap on emissions and obliging polluters to buy and sell permits to stay within it.

Under previous leader John Howard, the Liberal-led coalition had promised the "world's most comprehensive" carbon-trading scheme would be up and running by 2012.

"It would be an act of environmental suicide, an act of economic suicide, if Australia were to be so far in front of the world implementing an ill-considered, not yet properly developed and tested, emissions-trading scheme, if we haven't got a genuinely global response," Liberal leader Brendan Nelson said.

His back-flip fits a pattern that has seen the Liberals seek to win support by promising to do less to tackle climate change than the Rudd government.

The Liberals, swept from power in November, have also broken with previous policy and promised to cut excise tax to reduce the cost of petrol if they were to win back the government.

Nelson said the Liberals wouldn't have a definitive climate-change policy until as late as next year. "We would expect that from 2009 out of Copenhagen that there will be a global agreement," Nelson said.

"For Australia to go it alone well in advance of the rest of the world would do irreparable damage to our economic future and not do a darn thing to address climate change and an environmentally sustainable future for the planet," he said.

Nelson was a member of the Howard administration that for 10 years refused to sign the Kyoto Protocol on climate change. Rudd signed for Australia when he won office, set a target for energy from renewable sources and pledged to follow Europe and bring in carbon-trading by 2010. (dpa)