Whistler, British Columbia: The United States is making trade concerns related to China more difficult to deal with when Washington ignores World Trade Organisation rules in the case of steel and aluminum tariffs, according to a senior European Union official.

Speaking on the sidelines of a meeting of finance ministers and central bankers of the Group of Seven - the world's seven leading economies - European Commission vice-president Valdis Dombrovskis said such an approach made it tougher to bring China in line.

"The problem is that by taking that kind of unilateral action the US is undermining the principle of multilateralism in international trade, so it becomes more difficult to deal with other concerns - like trade and market access practices in China," Dombrovskis said.

The US has bypassed WTO procedures and imposed tariffs on imported steel and aluminum from Friday, hitting Canada, Mexico and the European Union, even though the steel and aluminum over-capacity stems mainly from China.

Washington cited national security reasons for the tariffs.  He said G7 officials expressed concern to US Treasury Secretary Steven Mnuchin during the session on trade that the U.S. tariffs posed a risk to global economic growth.