The price of benchmark Brent North Sea crude oil for February delivery was up US38 cents at $US31.60 per barrel in late deals, after earlier reaching $US31.80.
Prices on the New York Mercantile exchange reached $US33.55 per barrel in mid-day trading. The jump in prices came as Mr Blix warned Iraq it must do more to avoid the threat of war.
The price of oil has been climbing since Monday, despite an agreement by producers' cartel Opec to boost output.
Prices were initially pushed up by a cut in production in Venezuela because of a general strike. But the possibility of a war with Iraq has added pressure.
The markets think the OPEC production increase will not be enough to fill the gap.
