GENEVA — The handsome stone edifice that serves as the headquarters for the World Trade Organization rises like a fortress over Lake Geneva, projecting an air of impregnability. But lately the institution looks vulnerable, sowing worries that global commerce itself may be in jeopardy.

As the United States accuses China of predatory trading practices while doling out unilateral punishment, the trade organization tasked with preserving the peace appears marginalized.

The latest indication came on Thursday, when President Trump effectively bypassed the trading organization in announcing plans to impose tariffs on as much as $60 billion worth of Chinese imports, from electronics to running shoes. By Friday morning, China was threatening to retaliate with tariffs on some $3 billion worth of imports from the United States.

Diplomats and trade officials said the American action — if followed through — would flout W.T.O. rules, given that the United States would be imposing tariffs without first adjudicating its grievances. Chinese retaliation would similarly deviate from W.T.O. rules.