Syria and Nicaragua have joined the accord, which unites the world's nations in tackling climate change, leaving the U.S. to abstain. The effort was spearheaded by the Obama administration to codify an global commitment to ward off the impact of climate change.
However, the agreement doesn't set binding limits on emissions, and each country sets its own targets and is free to change them.
The US will soon become the only country that opposes the worldwide landmark climate change accord known as the Paris Agreement.
President Donald Trump, who has expressed doubts that man-made greenhouse gas emissions are the prime cause of global warming, announced in June that he meant to pull out and instead promote United States coal and oil industries. "At what point does America get demeaned?"
The war itself has caused an worldwide refugee crisis, which has enabled Islamic State militants to pose as refugees and enter into other countries.
According to Trump, the Paris accord would have cost the United States 6.5mil jobs and US$3tn GDP in lost, whilst conveying that the accord favours economy rivals in China and India.
Trump's decision was met with praise from Republican lawmakers and criticism from world leaders.
In June the USA said it would withdraw, but the rules of the agreement state that this can not be done until 2020.
It will then take one year to fully withdraw, meaning the earliest the United States could officially withdraw is the day after the 2020 election.
The only other previous holdout, Nicaragua, announced in September that it would join the pact.
Syria is also joining, and announced its move Tuesday at climate talks in Bonn, Germany, Der Spiegel reported.
The United Nations welcomed Syria's statement as a declaration of intent to adhere to the Paris pact.
"The December 12 summit aims to bring together key players in the world of climate and finance".
The Trump administration has not said what those terms might be. The other big feature on McKenna's personal Twitter account is never-ending happy stories about renewable energy and government programs to address climate change, so much so that you would never know the government she represents claims the world faces an imminent, existential threat from global warming in which hundreds of millions of people will soon die.
"It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century", the assessment stated.