US President Barack Obama has unveiled sweeping plans described by him as the "biggest, most important step we have ever taken" to tackle climate change.

The Clean Power Plan is the final version of regulations crafted by the Environmental Protection Agency (EPA) that is intended to reduce greenhouse gas emissions from the electric power sector on a state-by-state basis.

It includes incentive programmes for US states to adopt renewable energy sources such as wind and solar power.

"We're the first generation to feel the impact of climate change, and we're the last generation that can do something about it," Obama said unveiling the plans.

"Climate change is no longer about protecting the world for our children and grandchildren, it is about the reality that we are living with right now."

The plan targets cutting emissions from power plants by 32% by the year 2030 compared with 2005 levels – the equivalent of taking 166 million cars off the road.

However, it is likely to face legal challenges from several states and the multi-billion-dollar energy industry.

Scientists hold a near-unanimous consensus that the recent global warming trend is caused by increased concentrations of greenhouse gases in the atmosphere, driven mainly by human activity.

'Need to act now'

"This is one of those rare issues – because of its magnitude, because of its scope – that if we don't get it right, we might not be able to reverse, and we may not be able to adapt sufficiently," Obama said.

"There is such a thing as being too late when it comes to climate change."

Under the plan, each US state will have to comply with an emission-cutting target set by the EPA, but they will have flexibility in how best to achieve that goal.

Barack Obama
Barack Obama is hoping to secure a universal climate agreement at the UN summit in ParisJoshua Roberts/Reuters

While critics say complying with the new rules will cost industries billions of dollars, raise electricity prices and hurt the US economy, the White House claims they will save the average family $85 on their annual energy bill by 2030 and save consumers a total of $155bn between 2020 and 2030.

Coal power supplied 39% of US electricity in 2014, according to the US Energy Information Administration, compared to 27% from natural gas, 19% from nuclear power plants and 7% from renewable sources excluding hydroelectric plants.

More than 350 companies, including Nestle, Unilever and General Mills, wrote letters to 29 state governors across the US urging them to back the ambitious plans, but several leaders have already said they will simply ignore them.

One Republican presidential hopeful, Jeb Bush, denounced the plan as "irresponsible and overreaching".

"Climate change will not be solved by grabbing power from states or slowly hollowing out our economy," he said.

"The rule runs over state governments, will throw countless people out of work, and increases everyone's energy prices.

"The fact is, US emissions of greenhouse gases are down to the same levels emitted in the mid-1990s, even though we have 50 million more people.

"A chief reason for this success is the energy revolution which was created by American ingenuity – not federal regulations."

The Clean Power Plan boosts Obama's hopes to secure a legally binding and universal agreement on climate at the UN conference in Paris in November.

The US president pledged to double the pace of cuts in his country's carbon emissions in a landmark climate deal with China last year, reducing them to between 26% and 28% below 2005 levels by 2025, in return for Beijing committing to a peak year target of 2030 for its emissions.