• US West Texas Intermediate (WTI) crude futures were down 3pc, or 98 cents, at $31.83 a barrel at 0709 GMT.
• The US futures slipped earlier as much as 5pc  to a low of $31.14.
• Brent crude futures were down 2pc, or 71 cents at $34.03 per barrel, after dropping to as low as $33.63.

The decline in oil benchmarks extended losses from Wednesday over uncertainty about Russia's commitment to deep output cuts ahead of a June 9 meeting of the Organization of the Petroleum Exporting Countries and its allies, a grouping dubbed OPEC+.

US West Texas Intermediate (WTI) crude futures were down 3pc, or 98 cents, at $31.83 a barrel at 0709 GMT.

The US futures slipped earlier as much as 5pc  to a low of $31.14.

Brent crude futures were down 2pc, or 71 cents at $34.03 per barrel, after dropping to as low as $33.63.

"The rise in API (American Petroleum Institute) inventories was very much unexpected and means this evening's US EIA crude inventories will be monitored closely. That appears to be weighing on sentiment in Asia," said Jeffrey Halley, senior market analyst at OANDA.

Data from industry group API showed US crude stocks rose by 8.7 million barrels in the week to May 22, compared with analysts' expectations for a draw of 1.9 million barrels.

"With the oil market assumed to be rebalanced at a much quicker pace than anyone expected, investors are now attempting to digest the outcome of the upcoming OPEC+ meeting," said Stephen Innes, chief global markets strategist at AxiCorp.

"As is often the case during a run-up up an OPEC+ meeting, the focus is squarely on Russia's commitment and understandably so as historically they have been the laggard within the OPEC+."

With WTI holding above $30 a barrel, OPEC+ will be closely watching to see whether US shale oil producers, who have breakeven prices in the high $20 and low $30 dollar range, step up production, National Australia Bank's head of commodity research, Lachlan Shaw said.