US President Donald Trump found himself alone at the G20 summit over climate change, as the other 19 members described the Paris climate accord as 'irreversible'.

Theresa May said she was dismayed about Mr Trump's decision to pull out of the international agreement although she remains hopeful the UK's close ally may rejoin the accord.

The Prime Minister said she has urged the president to rejoin the agreement and raised it with him on the sidelines of the G20 gathering in Hamburg, although it was not one of the items on the agenda in the formal meeting between the two leaders.

Theresa May meets U.S President Donald Trump during the G20 summit on July 8, 2017 in Hamburg

The German Chancellor said decisions at the summit had been difficult, but said leaders had achieved 'good results'

She said: 'Like other world leaders here, I am dismayed at the US decision to pull out of the Paris agreement and I have urged President Trump to rejoin the Paris agreement.

'The UK's own commitment to the Paris agreement and tackling global climate change is as strong as ever.'

Challenged on why she had not used her bilateral meeting with the US president to tackle him on the issue, she said: 'I did bring the issue of the climate change agreement up with President Trump, I've had a number of conversations with him over the time I have been here at the G20.

'When I brought it up with him, what I did was I encouraged him to bring the United States back into the Paris agreement.

'I continue to hope that is exactly what the United States will do.'

German Chancellor Angela Merkel today described the US position as 'regrettable'.

She told reporters at the end of the two-day meeting: 'I think it's very clear that we could not reach consensus, but the differences were not papered over, they were clearly stated.'

Merkel described the decision by Donald Trump to leave Paris agreement on climate change as 'regrettable'

Merkel said she does not agree with British Prime Minister Theresa May, who yesterday claimed Washington could decide to return to the agreement, which aims to lower emissions of greenhouse gases.

At a closing press conference, Mrs May underlined the UK's commitment to the climate change deal.

'Not only will this protect the environment for future generations, it will keep energy affordable and maintain a secure and reliable supply in order to protect the interests of businesses and consumers,' she said.

'We play a leading role internationally and we are delivering on our commitments to create a safer, more prosperous future for us all.'

Critics of the US policy highlighted the splits within the international community, saying there was now a G19 committed to the Paris deal with Mr Trump on the outside.

But conservation groups demanded faster action to end the use of fossil fuels.

Greenpeace International executive director Jennifer Morgan, said: 'The G19 held the line, defending the Paris Agreement against Trump's backward decision to withdraw, but that is not enough.

'The G19 should have committed to accelerate the transformation away from coal, oil and gas. If Paris was the starting point, Hamburg must sow the seeds of much greater ambition.

'Millions of people suffering from the impacts of climate change are demanding urgent action to end the age of coal, oil and gas. To put words into action, the G19 must now accelerate the clean energy transition and set sail from Hamburg with an agenda of change.'

Pictured: Donald Trump waving as he boards Air Force One following the G20 summit in Hamburg

WWF climate and energy spokesman Manuel Pulgar-Vidal said: 'Implementing the Paris Agreement is in the interest of each nation.

'Effective climate strategies can help unlock new business and employment opportunities, renewable energy, health benefits, and a sustainable future for all.

'As G20 leaders join cities, companies and individuals around the globe in committing toward a climate-safe future, it must be crystal clear that there is no place for fossil fuels in this scenario. We can be stronger together for climate but we need to translate ambition into action now.'

Scientists believe these are responsible for global warming.

France's President Emmanuel Macron said he has not given up on Trump changing his mind on leaving the landmark 2015 Paris climate accord.

Saying that he 'never gives up hope on convincing' others, the French leader added that 'therefore I confirm that I hope to convince him'.

Leaders of the 20 largest economies in the world, including Trump, did reach a common statement about the other contentious issue at the summit - trade.

The statement retains the G-20's longstanding rejection of protectionism.

But it also acknowledged that trade must be mutually beneficial and that countries can use 'legitimate' trade defenses to protect workers and industries against being taken advantage of by trade partners.

Merkel said discussions at the summit today had been 'difficult', but said leaders had achieved 'good results in some areas'.

She said: 'I can only call things as they are.'

She pointed to a hard-won agreement on trade, one in which she said 'every word was weighed'.