In September, the WTO estimated that global trade would rise by 3.9 per cent this year, but lowered that projection to 2.8 per cent, in an updated forecast.
"Trade is still registering positive growth, albeit at a disappointing rate," WTO director general Robert Azevedo said in a statement.
Various factors were continuing to apply downward pressure on global commerce, the Geneva-based body said.
The rout on commodities prices has shown few signs of reversing, while the full extent of the slowdown in China -- the world's top commodities consumer -- remains uncertain.
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But, the 2.8 per cent growth forecast could prove to be an underestimate if efforts by the European Central Bank to stimulate eurozone growth are successful, the WTO said.
The organisation predicted that global trade would tick upwards by 3.6 per cent in 2017, on the back of increased demand for imported goods in Asia.
Azevedo issued a broad warning on "the threat of creeping protectionism, as many countries continue to apply trade restrictions.