The US government yesterday agreed to lend refiners small quantities of oil from its strategic emergency stockpile to help ease the shortage of petrol caused by Hurricane Katrina. But the relief it caused in the overheated oil market was cut short when it became clear that the move would have little impact on the problem and was as much a political gesture as an economic one.

In fact, helping the US deal with the loss of 20 per cent of its oil production and 10 per cent of its refining capacity has become a global tug of war between three powerful players.