The US Department of Agriculture (USDA) estimates production of 32,000 metric tonnes in 2006 - a drop from the unusually high 33,000mt recorded last year.
Numbers are down in France thanks to the recent summer heatwave which affected the quality and quantity of crops.
But despite the shortfall, the first seven months of the year saw a climb in production, according to the USDA report.
This was attributed to larger crops in 2005 and reduced competition of US walnuts in Germany, which is France's biggest export market.
The South East region contributed 16,800 mt to the overall French crop in 2005 while the South West harvested 14,200mt, resulting in figures significantly higher than the five-year average for the country.
Walnuts are enjoying increased popularity as part of the drive towards healthier snacking options.
Nuts are a good choice for healthy consumers as they contain vitamin E, folic acid - which aids energy release from foods - and minerals such as zinc, which helps strengthen the immune system.
And in several scientific studies, walnuts in particular have been found to contain 'bad' cholesterol-lowering fatty acids, linking them to the prevention of heart disease.
According to the Food and Agricultural Organisation of the United Nations (FAO), the world's top walnut exporter is China, which produced 420,000mt last year.
FAO figures show that France ranks seventh in terms of global production.