The world’s top oil fund, United States Oil ETF (NYSEARCA: USO), booked on Tuesday its biggest daily outflows since December 2016 amid heightened volatility ahead of the OPEC+ meeting which was scheduled for the coming weekend but has since been delayed.

USO saw daily withdrawals of nearly $225 million, according to estimates by Bloomberg.

United States Oil ETF has been the biggest and most closely watched oil-linked exchange-traded product on the market for years. USO seeks to reflect the performance of the spot price of West Texas Intermediate light, sweet crude oil delivered to Cushing, Oklahoma by investing in a mix of oil futures contracts and other oil interests.

USO became in late October once again the biggest oil exchange-traded fund in the world in terms of total assets, topping WisdomTree Brent Crude Oil fund for the first time since the beginning of this year.

In recent weeks, volatile oil prices have led to large inflows and outflows at USO and other commodity and cross-commodity funds, as the market is focused on demand concerns and on speculation about oil supply from OPEC+ next year.

The market is eagerly expecting the meeting of the producer group, which is set to decide on oil production levels for early 2024. Speculation is growing that Saudi Arabia could roll over its unilateral production cut of 1 million barrels per day (bpd) into at least the first quarter of 2024, which is typically a low season for global oil demand.

The current oil market deficit will turn into a slight surplus next year even if OPEC+ leaders Saudi Arabia and Russia extend their production and export cuts into 2024, according to Toril Bosoni, the Head of Oil Industry and Markets Division at the International Energy Agency (IEA).

Global oil stocks are currently falling “at a fast rate”, Bosoni told Reuters on Tuesday, but the agency expects a surplus on the market early next year.