Oil was on track for its biggest monthly drop in six months on May 31 as U.S. President Donald Trump ramped up trade tensions, weighing on the demand outlook.

Brent futures are heading for an 11% slide in May and WTI for a 13% drop, their biggest monthly losses since November.

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“No notice was taken of data that were positive for prices, whereas mildly disappointing figures put prices under considerable pressure,” Commerzbank analysts said.

“This selective reaction is typical of a climate of severe pessimism, as is the fact that market players are currently focusing only on demand worries while ignoring the fact that supply remains limited.”

Front-month Brent crude futures, the international benchmark for oil prices, were at $64.91 at 11:16 GMT, down $1.96 from last session’s close.

U.S. West Texas Intermediate (WTI) crude futures were at $55.31 per barrel, down $1.28 from their last settlement.

Both grades earlier hit their lowest since March 8.

U.S. President Donald Trump vowed May 30 to slap tariffs on all goods from Mexico unless it stops illegal immigration, firing up fears over economic growth and appetite for oil.

“The decision, understandably, is sending shivers down investors’ spines,” PVM said in a note. “U.S. refiners import roughly 680,000 barrels per day of Mexican crude. The 5% tariff adds an extra $2 million to the cost of their daily purchases.”

The Mexico trade dispute adds to a trade war between the U.S. and China, which many analysts expect to trigger a recession.

Chinas factory activity shrank more than expected in May, an official survey showed on May 31.

U.S. Output Back To Record

Crude prices have also been under pressure from a return in U.S. oil production  to a record 12.3 million barrels per day (MMbbl/d), and a much smaller than expected decline in U.S. stockpiles.

The U.S. Energy Information Administration (EIA) said crude stocks fell by around 300,000 barrels last week, to 476.49 MMbbl.

That was much less than the 900,000-barrel decline analysts had forecast in a Reuters poll, and well below the 5.3 MMbbl drawdown seen by the API industry body.

Giving a floor to prices, top oil exporter Saudi Arabia’s increased output in May was not enough to compensate for lower Iranian exports, which collapsed after the U.S. tightened the screws on Tehran, a Reuters survey found.

Washington will sanction any country that buys oil from Iran after the expiration of waivers on May 2, U.S. Special Representative for Iran Brian Hook said on May 30.

The Wall Street Journal had reported earlier on May 30 that countries like China and India that were issued waivers in November to buy Iranian oil could continue the purchases after May 2 until they reached a negotiated cap.