US President Donald Trump has reignited his spat with the world's largest oil producers as surging oil prices take their toll on US manufacturing.
Trump used Twitter to accuse the Organisation of Petroleum Exporting Countries (Opec) of being "at it again", in a fresh verbal attack on the cartel which he blames for the faster than expected oil price recovery.
The benchmark price of crude has surged from around US$50 ($71) a barrel last summer to within a breath of US$80 a barrel a few weeks ago.
The heady market surge is taking its toll on heavy-energy users in the US where the producer-price index rose by 0.5 per cent in May from a month earlier, according to the latest data from the US Department of Labour.
The report revealed that overall prices increased 3.1 per cent in May from a year earlier, the largest annual increase since 2012.
Prices excluding food and energy rose by 2.4 per cent and prices excluding food, energy and trade services climbed 2.6 per cent.
The higher than expected index hike emerged ahead of the summer driving season where motorists are also likely to be stung at the pumps.
"Oil prices are too high, Opec is at it again. Not good!", Trump told his 53 million Twitter followers.
The outburst follows a warning from the President earlier this year that "artificially very high" oil prices would not be accepted.
Trump said, via Twitter: "Looks like Opec is at it again. With record amounts of oil all over the place, including the fully loaded ships at sea, oil prices are artificially Very High! No good and will not be accepted!"
The latest warning comes days before a key make or break meeting of Opec and its allies.
Opec and non-Opec producers, led by Russia, will meet in Vienna late next week to decide whether the 17-month long pact to cut 1.72 million barrels of oil production a day should remain.