PARIS, Sept 8 (Reuters) - The United Nations food agency's world price index fell in August to a new two-year low, reversing a rebound seen the previous month, as a decline in most food commodities offset increases for rice and sugar.

The Food and Agriculture Organization's (FAO) price index, which tracks the most globally traded food commodities, averaged 121.4 points in August against a revised 124.0 for the previous month, the agency said on Friday.

The August reading was the lowest since March 2021 and also 24% below an all-time high reached in March 2022 in the wake of Russia's invasion of Ukraine.

In a separate report on cereal supply and demand, the FAO forecast world cereal production this year at 2.815 billion tonnes, down slightly from a previous estimate of 2.819 billion.

The revised forecast was nonetheless up 0.9% on 2022 and matched record output from 2021, the FAO said. (Reporting by Gus Trompiz; Editing by Hugh Lawson)