World food prices were largely stable in August from the month before, with a rise in wheat prices offset by declines in sugar, vegetable oils and dairy indices, the United Nations food agency said on Thursday.

The Food and Agriculture Organisation's (FAO) food price index, which measures monthly changes for a basket of cereals, oilseeds, dairy products, meat and sugar, averaged 167.6 points last month, against a downwardly revised 167.2 in July.

The July figure was previously given as 168.8.

FAO said global cereals output in 2018 was seen at 2.587 billion tonnes, down 64.5 million tonnes, or 2.4 per cent, from 2017's record production level. FAO's forecast for world wheat production in 2018 was cut by 1.9 per cent since July and now stands at almost 722 million tonnes, the smallest since 2013.

The drop in wheat production, blamed largely on a heatwave in Europe, has pushed prices for this crop up some 8 per cent month-on-month, the largest rise for any of the FAO indices.

By contrast FAO's sugar price index dropped 5.4 per cent from July, the lowest level in a decade. The decline was largely due to the continued depreciation of the currencies of Brazil and India against the US dollar, FAO said.