Oil output from OPEC fell in May, hitting a five-year low as the group warned that U.S.-China trade tensions could lead to slower economic growth and weak fuel demand.

Production from the 14-nation producer club fell by 236,000 barrels per day last month to 29.88 million bpd, according to independent sources cited by OPEC in its monthly report. It was the first time OPEC pumped below 30 million bpd since June 2014.

The slump in production comes as OPEC is considering whether to extend a six-month deal to hold down output. In the monthly report, OPEC says it will carefully consider the economic outlook when it meets with Russia and other oil-exporting nations in coming weeks.

"Throughout the first half of this year, ongoing global trade tensions have escalated, threatening to spill over, and geo-political risks remained in many key regions," OPEC said. "This has resulted in a slowdown in global economic activities, and weaker growth in global oil demand, both compared to a year earlier."