Dubai (CNN Business) OPEC is losing one of its oldest members.

The small, gas-rich state of Qatar said Monday that it will leave the oil cartel on January 1 after nearly 60 years. The country's state oil company, Qatar Petroleum, made the announcement in a series of tweets.

"The withdrawal decision reflects Qatar's desire to focus its efforts on plans to develop and increase its natural gas production," Saad Sherida Al-Kaabi, the country's newly-appointed minister of state for energy affairs, was cited as saying in one of the tweets.

Qatar has been under a diplomatic and economic embargo by its Arab neighbors, including OPEC members Saudi Arabia and the United Arab Emirates, for the past 18 months. In response, Qatar has been increasing gas production , the mainstay of its economy.

Qatar's newly appointed energy minister, Saad Sherida Al-Kaabi. He announced on Monday that Qatar will be withdrawing from OPEC in January.

OPEC has no role in the global market for natural gas. And Qatar made no reference to the dispute with other Gulf states in its announcement, emphasizing plans to cement its position as the world's leading supplier of gas. Its exports currently account for about 30% of global demand.

Read More