Top US importers are stocking up on Chinese goods before new import tariffs take effect, shipping giant AP Moller-Maersk said today.

But the company warned that a trade war would hit demand for container shipping in the coming years. 

Maersk's data indicated that imports into the US from China had grown 5-10% year-on-year in the third quarter as companies such as Walmart and Home Depot built up inventories to avoid new import tariffs, chief executive Soren Skou said. 

"The irony is that after (US President Donald) Trump has turned up the rhetoric, the US has started importing even more from China," Skou told reporters. 

"But there will definitely be a price for the container industry to be paid," he said, noting that the recent spike in shipments would be followed by a slowdown next year. 

Chinese imports from the United States were down 25-30% in the third quarter compared to last year, Maersk shipping data indicated. 

Maersk is the world's biggest container shipper with around 750 vessels. 

The effect of trade tensions could reduce global container trade by between 0.5% and 2% in 2019 and 2020, Maersk said as it presented results for the July-September quarter. 

Container shipping volumes, excluding those from Hamburg Sud, were weaker than expected, falling by 1.9%from the previous quarter.

The company sold Maersk Oil to French energy major Total in a $7.5 billion deal last year, and said in August it would spin off its offshore drilling operation and list it in Copenhagen next year. 

However, selling its oil and gas business has made it more reliant than ever on the shipping industry and swings in freight rates and fuel oil prices. 

Maersk narrowed its expectation for full-year earnings before interest, tax, depreciation and amortisation (EBITDA) today to $3.6-4 billion from $3.5-4.2 billion previously. 

EBITDA totalled $1.14 billion for the quarter, topping the $1.09 billion forecast by analysts in a Reuters poll. 

Maersk bought German rival Hamburg Sud in 2016, which helped it boost revenue in the quarter by 31% from a year earlier to $10.08 billion versus the $9.98 billion expected by analysts. 

However, unit costs rose by 1.5% to $1,809 per 40-foot container from the previous quarter.