China has overtaken Canada as the United States' largest trading partner, as the low price of oil eats into the value of Canadian energy exports.

U.S. Commerce Department data show trade in goods with China hit $441.7 billion US in the nine months to September, up 3.7 per cent since last year.

But Canada's trade with the U.S. was $438.1 billion for the same period, down 11.6 per cent from the previous year.

Most of that drop was because of crude oil, with the price being half what it was in 2014.

Statistics Canada reports a 32 per cent drop in the value of Canada's trade in energy products in September alone compared to the previous year.

The U.S. remains the largest trading partner by far of Canada, accounting for $261 billion in exports and $234 billion in imports over the first nine months of the year. China is a distant second.

China imported $357 billion in goods to the end of September, even with a strong U.S. dollar and a devalued Chinese currency.

China is equally reliant on the U.S. consumer to buy its manufactured goods, as demand from most of the world has waned.