Syria has pledged to sign up to the Paris accord on climate change, leaving the United States the only country opposed to the pact.

The Arab state, in the midst of a bloody six-year-war, on Tuesday became the final functioning state to commit to try to lower temperature rises.

"I would like to affirm the Syrian Arab Republic's commitment to the Paris climate change accord," Wadah Katmawi, deputy Environment Minister, said on the second day of climate talks in Bonn, Germany.

Nicaragua had been the only other country outside the 195-nation agreement, which it criticised as “too weak”, until it signed up last month.