Belgium abstained because the regional government of Wallonia, a French-speaking area in the south, viewed the negotiations much like France, according to a Belgian diplomat, who declined to speak on the record given the continuing negotiations.

In 2016, Wallonia temporarily blocked the ratification of a free-trade deal between the European Union and Canada, on both protectionist and environmentalist grounds.

The two negotiation mandates were first proposed in January by the European Commission, which negotiates trade deals for the bloc’s 28 member states.

Last year, Mr. Trump imposed tariffs on steel and aluminum produced in the European Union. The European Union retaliated with tariffs on a list of goods imported from the United States. In July, leaders on both sides called a truce during a meeting in Washington and vowed to work toward a free-trade agreement.

However, Congress has made clear that it will not ratify any trade agreement with the European Union that doesn’t include agriculture. And the Trump administration has repeatedly insisted that agriculture be included in later negotiations, something that European countries, including France, have forcefully resisted. Meanwhile, the United States has been threatening to impose punitive tariffs on European car imports.

Peter Chase, a former United States trade representative in Brussels and currently a resident senior fellow at the German Marshall Fund, said: “The U.S. administration is trying to push Europeans to adopt a negotiating mandate using the threat of the auto tariffs to ensure that mandate is broad and includes agriculture. The U.S. will push, and the E.U. will push back.”

“I do think that it is possible that the U.S.-E.U. trade relationship will become more contentious over the next few months,” he said.