BRUSSELS — The top American agriculture official on Tuesday called on the European Union to do more to ease restrictions on gene-altered food and feed crops if it hoped to reach a trans-Atlantic trade pact.

“There can’t be a trade agreement without a serious and significant commitment to agriculture,” the official, Agriculture Secretary Tom Vilsack, told reporters on Tuesday, a day after an informal meeting with European farm ministers. European consumers “ought to have a choice” whether to use biotech foods, he said.

Mr. Vilsack has a tough case to make, though. There continues to be deep resistance to bioengineered agricultural products in the European Union — or to easing many other agricultural trade protections, for that matter. The fight over food, in fact, is a big impediment to progress in talks that are already moving more slowly than officials on both sides had wanted when President Obama announced them last year.

Negotiators are trying to reach a Trans-Atlantic Trade and Investment Partnership, an agreement that goes far beyond cutting import duties by creating a more uniform market and by synchronizing regulations for products like automobiles and medicines. But after five rounds of meetings, the negotiators are at odds in important areas, including how to lower tariffs, whether to include financial services in any deal, and how to create freer trade in food and farming.