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Global goods trade will grow by 3.3 percent this year and by 4.0 percent in 2016, less than previously forecast, mainly due to sluggish economic growth, the World Trade Organization (WTO) said on Tuesday.

WTO Director-General Roberto Azevedo said there were a number of factors including oil prices, currency volatility, monetary policy and the slowdown in major emerging economies that were factored into the revisions, as he warned that more downgrades could follow.

"There were a number of unexpected trade numbers that forced us to revise these numbers down," Azevedo told CNBC on Tuesday.

"We had oil and commodity prices going down, which bring the numbers of trade expansion down. Monetary policy is diverging between the U.S. and the EU (European Union), which means that big shifts in capital flows and currency values may be affecting trade as well," he added.

Azevedo then said: "We could have further downward revisions, that's for sure – most of the risk factors that we have are of a downward nature – so its really unpredictable at this point in time. It doesn't look like we are going to go back to the 5 percent level that we had in the 1990s, or before the crisis even, anytime soon."

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The WTO figures are based on economic growth estimates from organisations including the International Monetary Fund, which also updated its forecast on Tuesday.

WTO Chief Economist Robert Koopman said the new IMF figures would be "in the same ballpark" and would not affect the WTO's forecast.