UPDATE 1-Norway trims 2008 oil and gas output forecast

(Adds comments on oil price, investments)

OSLO, May 15 (Reuters) - Norway's Labour-led government trimmed its 2008 oil production forecast to 2.4 million barrels per day from a previous projection of 2.5 million bpd, according to the revised budget for this year published on Thursday.

"Oil production is expected to continue to decrease gradually in the coming years," the Petroleum and Energy Ministry said in a statement with the revised budget.

The government of the world's fifth-biggest oil exporter and Western Europe's biggest gas exporter cut its projection for 2008 gas sales to 100 billion cubic metres from 108 bcm seen in October. The 2008 level is nonetheless 10 percent above 2007.

Next year gas sales are seen up to 110 bcm, it said.

The revised budget increased the average price of Norwegian crude oil in 2008 to 500 Norwegian crowns ($98.70) per barrel from a previous 360 crown forecast made last October. Next year it sees prices at 400 crowns per barrel.

"There is a considerable uncertainty inherent in the future oil prices," the ministry said.

"The weakening of the U.S. economy contributes to a reduction in demand for oil. On the other hand there is little spare capacity and uncertainty linked to the supply of oil from several countries," it said, adding that increased capital flows into oil and other commodities had also impacted the oil price.

This year's oil production is set to be the lowest since the mid 1990s and output is widely expected to continue to dip in future years due to depletion of ageing North Sea oilfields, some of which started pumping out oil in the late 1960s.