OPEC agreed Thursday to extend its deal to cut oil output by nine months, an OPEC delegate told Reuters, as the organization works to curb excess supply of crude oil that has kept prices low for three years.

Khalid Al-Falih, Saudi Arabia's energy and oil minister, told CNBC before entering the closed-door meeting of 14 countries in Vienna: "Nine months with the same level of production that our member countries have been producing at is a very safe and almost certain option to do the trick."

Why this isn't surprising: Last week, Saudi Arabia and Russia teamed up and announced they backed an extension in cuts to production. Their support for a deal encouraged other countries to rally behind them, and yesterday the Joint Ministerial Monitoring Committee announced that OPEC was close to a deal.