US crude oil production this year is expected to fall below 5 million barrels per day for the first time since shortly after World War Two, the government's top energy forecasting agency said.

The lower output is due to hurricanes Gustav and Ike, which at one point shut in almost all the 1.3 million barrels a day in oil production in the Gulf of Mexico, according to the US Energy Information Administration.

About 45 percent of Gulf oil output is still offline weeks after the hurricanes struck.

In its latest monthly forecast, the EIA said combined offshore and onshore US oil production should average 4.96 million barrels per day this year, down 100,000 barrels per day from last year and the lowest level since 1946.

Oil output is forecast to recover to 5.29 million barrels a day in 2009, but will still be far from US peak production of 9.6 million barrels a day in 1970, the EIA said.-Reuters