Oil prices weakened slightly on Thursday ahead of the release of the weekly report by the US Energy Department on the country’s energy reserves.

Report informs citing Interfax that estimates by the American Petroleum Institute (API) released on May 29 showed the largest decline in US oil inventories since late December last week – by 6.49 million barrels.

The Energy Department will publish its data on reserves later on Thursday.

July Brent crude futures fell by $0.15 (0.18%) on the London ICE Futures exchange to $83.45 a barrel.

July WTI futures fell by $0.12 (0.15%) in electronic trading on the New York Mercantile Exchange (NYMEX) to $79.11 a barrel.