A senator crucial to Australia's plans for carbon trading said on Wednesday he did not believe climate change was real, delivering what could be a fatal blow to government plans to slash industrial gas emissions.

Just a day after the upper house moved to delay debate on the emissions trading regime until August, independent Senator Steve Fielding said he had yet to see conclusive evidence of climate shift during days of closed-door government briefings.

Prime Minister Kevin Rudd needs Fielding's backing to get his centre-left government's laws endorsed by a hostile Senate and aims to begin carbon trading in mid-2011 to help cut Australia's large per capita output of carbon emissions.

But Fielding, a social and pro-family conservative, released a statement saying he was unwilling to risk thousands of livelihoods with "sky rocketing electricity prices and job losses on unconvincing green science".

Conservative opposition lawmakers holding the largest Senate voting bloc struck a deal on Tuesday with two independents, including Fielding, to effectively delay a vote until August in a move the government lambasted as a political stunt.

"This is a commitment that we gave the Australian people because this is what the Australian people asked for," Climate Change Minister Penny Wong said on Wednesday.

"People can see the evidence. They know what scientists have been telling us," she said.

Australia's carbon trading scheme aims to be the world's broadest, covering 75 percent of industrial emissions and 1,000 of the largest polluters, from transport operators to resource firms and aluminium makers.

As the world's biggest coal exporter, the country accounts for 1.5 percent of global carbon emissions but is amongst the highest per head polluters due to reliance on coal for 80 percent of domestic electricity.

Fielding said he did not believe any politician could vote for the scheme it its current form, while the government has refused to compromise on its target of a 25 percent cut on 2000 emissions levels if the world agrees to tough action during December global climate talks in Copenhagen.

The other independent, Senator Nick Xenophon, will on Thursday move formally for the Senate to vote on the emissions laws on August 13, after more studies on their economic impact.

Rudd discussed climate change on Wednesday with U.S. President Barack Obama, who a day earlier announced progress toward quick passage of legislation to fight global warming by reducing industrial carbon dioxide emissions.

Obama is backing legislation to cutting carbon dioxide emissions by 17 percent by 2020 and 83 percent by 2050 from 2005 levels.