World food prices rose slightly in September, approaching levels reached during the food crisis in 2008, the United Nations' food agency said on Thursday, trimming its forecast for global cereal output marginally.

The worst drought in more than 50 years in the United States sent corn and soybean prices to record highs over the summer, and, coupled with drought in Russia and other Black Sea exporting countries, raised fears of a renewed crisis.

The FAO Food Price Index, which measures monthly price changes for a food basket of cereals, oilseeds, dairy, meat and sugar, averaged 216 points in September, up 3 points from the reading in August, the FAO said in its monthly update.

The rise reflected mainly higher dairy and meat prices, with more contained increases for cereals, it said.

The Rome-based agency said it had cut its 2012 world cereals output forecast by 0.4 percent to 2.286 billion metric tons from a previous estimate of 2.295 billion metric tons, mainly due to a smaller maize crop in central and southeastern parts of Europe, where yields have been hit by prolonged dry conditions.

(Reporting By Catherine Hornby)