In ruling Tuesday, a federal judge sided with federal regulators, temporarily blocking the merger of two national grocery giants and stopping the sale of some Harris Teeter stores.

The Federal Trade Commission, along with nine states including Maryland, filed a lawsuit in February challenging Kroger Co.’s $24.6 billion bid to purchase Albertsons Companies Inc. The plaintiffs alleged the merger would reduce competition and lead to higher prices for millions of Americans.

Kroger’s plan to merge with Albertsons originally included a condition that it sell 10 of its Harris Teeter stores in Maryland, Virginia and Washington, D.C., to C&S Wholesale Grocers, a private wholesale grocery supply chain that operates Grand Union grocery stores and the Piggly Wiggly franchise.

In her ruling after a three-week hearing, U.S. District Court Judge Adrienne Nelson said the merger should be paused while an in-house administrative judge at the FTC more fully vets its implications.

“Any harms defendants experience as a result of the injunction do not overcome the strong public interest in the enforcement of antitrust law, especially given the difficulty in disentangling a premature merger,” Nelson wrote in her opinion.

The Associated Press contributed to this article.