The deal calls for state-owned Korea Gas Corporation to purchase 2 million tons of the fuel annually for two decades starting in 2013.

The agreement adds to existing supply deals, meaning Qatar will soon be supplying South Korea a total of 9 million tons of the fuel annually.

Financial terms weren’t disclosed.

Qatar holds the world’s third-largest reserves of natural gas.

Qatar has emerged as the biggest supplier of liquefied natural gas, a super-cooled form of the fuel condensed for easier transport aboard tanker ships.