Brent crude oil prices fell more than 2.1 percent in early Monday trading to $62.50 per barrel. West Texas Intermediate, the U.S. benchmark, lost 1.6 percent to $58.98 per barrel. Both indices are below the price at which they started the month.

Oil prices were lifted by upbeat forecasts on global demand from the Organization of Petroleum Exporting Countries last week. Optimism about the health of the world economy has helped oil prices recover from lows below the $50 per barrel mark in early 2015, though concerns about the pace of economic growth has throttled some of the momentum.

A failing Greek economy created waves across Europe at the height of the global economic crisis. With the status of latest round of negotiations uncertain, the International Monetary said "tough choices" need to be made by all parties for the sake of the community.

In the Middle East, U.N. Secretary-General Ban Ki-moon kicked off talks in Geneva aimed to resolving a simmering crisis in Yemen.

A briefing from the U.S. Energy Information Administration said port activity in Yemen may be the greatest security interest for the regional energy sector. Threats to the Bab el-Mandab shipping channel, through which more than 3 million barrels of oil passes per day, means shippers would have to go around the southern tip of Africa.

Yemen's conflict also pits Iran, a Shiite country supporting the Houthi rebel movement in Yemen, against Saudi Arabia, a Sunni ally of the Yemeni government. Iran and Saudi Arabia are both members of the Organization of Petroleum Exporting Countries with a keen interest on production levels.