One of the key engines of the world economy - global trade - looks increasingly precarious as leading indicators point to a meaningful slowdown next year, according to the chief economist of the World Trade Organisation (WTO).

"When you look at those leading indicators, they continue to weaken. It's almost like a death from a thousand cuts," Mr Robert Koopman said in an interview on Thursday. "There's not any one big change in those leading indicators but, boy, they are starting to add up."

Financial markets have been increasingly concerned about a possible slowdown in the world economy next year and the impact of US President Donald Trump's trade wars. Federal Reserve chairman Jerome Powell on Wednesday pointed to investor and business fears over trade tensions and global growth going into next year.

FedEx and other companies have also warned of being hit by slower economic growth.

The WTO in September downgraded its growth forecast for trade, predicting the volume of goods moving worldwide would expand by 3.9 per cent this year and slow to 3.7 per cent next year.

Mr Koopman said the organisation was holding to those forecasts for now, though he added that risks were rising that they could be downgraded again early next year.

A WTO tracker of leading indicators such as purchasing managers' indexes from around the world and air and sea freight points to slowing global trade momentum, he added.

"If we have an expectation that it is going to move in any direction, it's going to be down," Mr Koopman said of the 2019 projections.

He added that the biggest concern is not over the direct impact of the tit-for-tat tariff wars that the US has engaged in, most prominently with China but also with allies from the European Union to Canada. Though the US and China account for almost 40 per cent of global output, the goods traded between the world's two largest economies make up less than 3.2 per cent of global trade, according to the WTO.

Instead, Mr Koopman said, the real risk is how those trade conflicts could weigh on businesses and consumer sentiment and spending worldwide. What the world is waiting to see, he added, is: "Does the uncertainty - the policy uncertainty raised by this conflict - spill over into investment and consumer behaviour."

There are some initial signs that business investment is being hit and that consumers in both the US and China are starting to hold back on purchases, Mr Koopman said.

"It isn't a disaster yet," he added. "It's weak, but if we start to see a downturn, real declines in investment, that could be pretty problematic for global trade and global growth in general."