WASHINGTON — Canada has filed a sweeping trade case against the United States at the World Trade Organization, lobbing a diplomatic grenade at the Trump administration’s “America First” approach amid an increasingly embattled trade relationship between the longstanding North American allies.

The trade case could exacerbate tensions between the two nations, which have frayed in recent months as the countries wrestle with trade disputes and attempts to renegotiate the North American Free Trade Agreement. Canada’s case challenges the United States’ use of tariffs to punish unfair trade practices and protect its markets, saying those actions violate World Trade Organization rules.

The case could expand into a multinational trade dispute given that Canada, a champion of global agreements, filed it in a way that allows other countries to join. The 37-page document outlines numerous problematic trade actions that it says the United States has taken against China, South Korea, Japan and Germany.

The case, which was filed on Dec. 20 and made public on Wednesday, centers on the punitive tariffs that the United States imposes when it finds other countries guilty of subsidizing their products or of selling them abroad at unfairly low prices, a practice known as dumping. The United States has lost cases in the World Trade Organization over this system, which differs substantially from that of many countries.