Saudi Arabia rejected an OPEC plan to forge an agreement to freeze output at January levels, despite pressure from countries such as Qatar and Kuwait.
An agreement to freeze production would have likely helped to boost the oil price.
At its heart, this is a dispute between Saudi Arabia and Iran, which didn't even attend the meeting.
Iran has begun selling oil again after years of sanctions and is against curbing production and, as a result, crude oil tanked by nearly 5% on Monday, recovering from a 7% fall in early trading.
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