The day before the City Council passed the measure, a Walmart official warned in an op-ed article in The Washington Post that if required to pay $12.50 an hour, the company would cancel three planned stores and consider withdrawing from three projects already under construction.

The next move is up to Mayor Gray, who is weighing a veto.

Officially the mayor has taken no position, but he is widely seen as opposed to the measure. The Council has delayed formally sending it to his desk for action. The measure, called the Large Retailer Accountability Act, would require stores of at least 75,000 square feet that are owned by companies with $1 billion or more in annual revenue to pay the higher minimum wage. Because existing stores and those with unions are exempt, it is seen as squarely aimed at Walmart.

As Walmart, the world’s largest retailer, has sought inroads in major cities, it has faced resistance from local merchants, who fear being undercut, and from officials who say minimum-wage jobs mire workers in poverty.

Democrats on the House of Representatives work force committee produced a report this spring contending that the government subsidizes Walmart because employees earn so little that they qualify for Medicaid, food stamps and housing assistance.

Pedro Ribeiro, a spokesman for Mayor Gray, argued the opposite: minimum-wage jobs help the chronically unemployed take a first step into the work force.

“Yes, Walmart jobs are not great,” Mr. Ribeiro said. “But for some people, it will be their first employment and they’re not qualified to do anything else. We need that entry-level benchmark in the District.”