WASHINGTON — The U.S. share of world wheat exports was forecast to decline steadily in the next 10 years, largely because of expanding exports by nations of the former Soviet Union, according to long-term agricultural projections released Feb. 11 by the U.S. Department of Agriculture.

The U.S.D.A. in its U.S.D.A. Agricultural Projections to 2022 forecast the U.S. share of world wheat exports in 2022-23 at 15.6% compared with a projected share of 22.6% in 2012-13. In contrast, the share of world wheat exports for the nations formerly comprising the Soviet Union (most prominently Russia, Ukraine and Kazakhstan) was forecast to reach 30% in 2022-23 compared with the 18% share forecast for the current year.

“The strong upward trend in wheat exports from Russia, Ukraine and Kazakhstan was interrupted by droughts in 2010 and 2012,” the U.S.D.A. said in commentary accompanying the wheat trade data. “However, exports from these countries are expected to recover and rise more than 55%, climbing to nearly 50 million tonnes, by 2022 and accounting for about 80% of the projected increase in world trade. Increasing domestic feed use prevents even more rapid export growth.”

The U.S.D.A. added a caveat. “Although not explicitly reflected in the projections, continued year-to-year volatility in production and trade is likely because of the region’s highly variable weather and yields,” the U.S.D.A. said.

In terms of tonnage, U.S. wheat exports in 2012-13 (data in the long-term projections were based on the U.S.D.A.’s November outlook) were forecast at 29.9 million tonnes, up from 28.6 million tonnes in 2011-12. U.S. exports were forecast to drop to 27.2 million tonnes in 2013-14 and to 25.2 million tonnes in 2014-15. U.S. exports after 2014-15 were forecast to range between 25.3 million tonnes to 25.6 million tonnes annually through the rest of the projection period.