In a speech last week, Janet L. Yellen, the Treasury Secretary, said the pandemic and war had revealed that US supply chains, while efficient, were neither safe nor resilient. While warning against “a totally protectionist orientation”, she said the United States should work to reorient its trade relationship towards a broad group of “trusted partners”, even if it meant slightly more costs. high for businesses and consumers.

Ngozi Okonjo-Iweala, director-general of the World Trade Organization, said in a speech on Wednesday that the war had “rightly” added to questions about economic interdependence. But she urged countries not to draw the wrong conclusions about the global trading system, saying it had helped boost global growth and provided countries with important goods even during the pandemic.

“While it is true that global supply chains can be subject to disruption, trade is also a source of resilience,” she said.

The WTO has opposed export bans since the early days of the pandemic, when countries, including the United States, began imposing restrictions on the export of masks and medical products and did not remove them. phased out only gradually.

Now, the Russian invasion of Ukraine has triggered a similar wave of food-focused bans. “It’s like déjà vu,” Mr. Evenett said.

Protectionist measures have spread from country to country in a particularly obvious way with regard to wheat. Russia and Ukraine export more than a quarter of the world’s wheat, feeding billions of people in the form of bread, pasta and packaged food.

Evenett said the current wave of wheat trade barriers began as warring parties Russia and Belarus clamped down on exports. Countries along a major trade route for Ukrainian wheat, including Moldova, Serbia and Hungary, then began restricting their wheat exports. Finally, major importers concerned about food safety, such as Lebanon, Algeria and Egypt, have implemented their own bans.