Global trade volumes are set to grow by just 1.7 percent this year, the first time in 15 years that international commerce has grown more slowly than the world economy, the World Trade Organization said on Tuesday.

The forecast, much lower than the WTO's previous estimate of 2.8 percent in April, reflects a slowdown in China and Brazil and also decelerating imports in the United States.

The WTO also expects slower 2017 trade growth than its previous forecast, with a rise of 1.8-3.1 percent rather than the 3.6 percent it had estimated in April.