BRUSSELS — The executives came from companies that own brands like Nike, Levi’s and Zara.

They gathered here last month in a hearing room operated by the European government, for a public briefing on the status of trade talks between Vietnam and the European Union, which began last year. One industry noticeably dominated the audience, from the 14 chairs reserved for the European Branded Clothing Alliance, a trade group for the likes of H&M and Ralph Lauren, to the leader of an alliance of textile makers seated a few rows behind them.

For clothing and shoe companies, the negotiations between Europe and Vietnam are being watched with especially close care. Part of the reason is Vietnam’s role as an assembly line for much of the apparel worn in the Western world. Another is that Vietnam’s population also recently topped 90 million. Because the number of young people in the country is rapidly increasing, it has become an attractive growth market for apparel makers.

The most contentious issue, though, relates to a continuing push by the fashion industry to ease global “rules of origin.” Such rules establish where customs collectors consider a product is made. The standards are stricter in the United States than in Europe — indeed, the issue is also part of negotiations between the United States and Asia — but the fashion industry hopes that a change in rules in one jurisdiction could weigh on the larger negotiations among the giant trading blocs.

For goods coming into the European Union from Vietnam, the rules of origin can add up to substantial sums of money.