US President Donald Trump has again denounced the Paris climate accord, during a speech on America's environmental leadership.

He described the accord as being "ineffective and very, very expensive".

Two years ago, Mr Trump announced that the United States was pulling out of the 2015 Paris agreement, which aims to limit global warming well below 2C.

Last year, Mr Trump said he did not believe a report from his own government warning of massive economic losses if carbon emissions continue to feed climate change unchecked.

Mr Trump has promoted the use of fossil fuels, eased environmental regulations and tried to unwind more stringent fuel standards for vehicles.

In his speech, Mr Trump did not mention climate change and claimed signatories to the Paris accord lag behind the US in terms of emissions reduction.

"We will defend the environment but we will also defend American sovereignty, American prosperity, and we will defend American jobs," he said.

Denouncing what he called "a relentless war on American energy" under the previous administration of Barack Obama, Trump forcefully rejected "radical plans" in the struggle against climate change which, according to him, "would not make the world cleaner".

Reacting on Twitter, former vice president Al Gore said Trump "is refusing to see reality."

Mr Gore, co-winner of the 2007 Nobel Peace Prize for his activism on climate change, said that "American voters are not fooled by the president's attempts to cover up his failed environmental record".

In October, a landmark United Nations report warned that time is running out to avert disaster and that avoiding global climate chaos will require an unprecedented transformation of society and the world economy.

Mr Trump has repeatedly questioned environmental science and claimed earlier this year that climate change "goes both ways".