Lockdowns in China are having greater impact on global supply chains than the war in Ukraine and will be felt even after they are lifted, said the head of Deutsche Post DHL Group's freight business.

China renewed COVID-19 lockdowns in major centers in March and April, hitting production and consumption and heightening risks for parts of the global economy heavily dependent on the country.

"After an opening, traffic jams will probably form in front of U.S. and European ports," DHL's Tim Scharwath told Reuters, adding that "it will take longer than we had thought until the trade system normalizes again."

He said that global supply chain problems would probably continue beyond the crucial Christmas shopping season and into next year.

"China is the workbench of the world," Scharwath said. "All goods from high-tech to fashion are affected by the developments in Shanghai," he said, adding that the speed with which China lifts all restrictions will be crucial.

Shipments normally arrive in Europe and North America little by little, Scharwath said, adding that a flood of containers could overwhelm ports unless China ends the lockdowns gradually.