West Texas Intermediate crude hit $135.09 in early trading on the New York Mercantile Exchange before falling to about $133 on profit taking.

The price of crude has now risen by one-third since the turn of the year, with traders blaming the most recent leap on a report showing that US energy inventories fell unexpectedly last week.

Investment bank Barclays Capital says Opec’s current reluctance to increase supply may see prices increase further.

“With growing fears over future market tightness largely dominating price dynamics at present, Opec’s market management in the short-run does not seem enough to us to reverse the recent strength in prices,” says Barclays.

The Paris-based International Energy Agency (IEA) has piqued the market’s interest by saying it may cut its long-term projection for crude supply after studying depletion rates at the world’s 400 largest oil fields.

The IEA is working with energy consultancies and the US Geologic Survey to compile data which will be released in November.