UNITED NATIONS (Reuters) - Syria has formally jointed the 2015 Paris deal aimed at slowing climate change, the United Nations said on Tuesday, leaving the United States as the only country opposed to the pact.

Syria, racked by civil war, and Nicaragua were the only two nations outside the 195-nation pact when it was agreed in 2015. Nicaragua’s left-wing government, which originally denounced the plan as too weak, signed up last month.

Syria announced last week that it intended to join.

U.N. spokesman Stephane Dujarric told reporters in New York that Syria had submitted instruments of accession to the Paris climate deal and that the move would enter into force for the country on Dec. 13.

U.S. 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 intended to pull out and instead promote U.S. coal and oil industries.

Overall, the Paris agreement seeks to limit a rise in temperatures to “well below” two degrees Celsius (3.6 Fahrenheit) above pre-industrial times, ideally 1.5.

The U.N.’s weather agency said on Monday that this year is on track to be the second or third warmest since records began in the 19th century, behind a record-breaking 2016, and about 1.1 Celsius (2F) above pre-industrial times.