By Peter Evans And Annie Gasparro 

European grocery chains Royal Ahold NV and Delhaize Group--which generate about 60% of their sales in the U.S.-- said they are discussing a merger that could create one of the largest supermarket operators in North America.

The companies gave no details in their brief statements confirming the talks following European media reports. A combined company would be valued at EUR22.91 billion, or $25.79 billion, based on closing share prices Friday, before reports of a deal surfaced.

Other retailers have bulked up recently in the U.S., where increased scale has become crucial for growth and improved profitability. Netherlands-based Ahold and Belgium-based Delhaize, which had combined revenue last year of around EUR54 billion, or $60.5 billion, generate most of their sales in the U.S., primarily with stores stretching along the East Coast. Ahold operates the Stop & Shop and Giant chains, as well as the online grocery store Peapod, while Delhaize owns Food Lion and Hannaford.

An Ahold and Delhaize combination would create the fourth-largest seller of groceries in the U.S. with about $46 billion in sales in the country last year, or 4.6% of the market, according to Euromonitor International, and about 2,000 total U.S. supermarkets. It trails Wal-Mart Stores Inc., which has 4,500 U.S. stores, Kroger Co., which has about 2,600, and Albertsons-Safeway, formed in a merger in January, with about 2,200 stores.

Traditional supermarkets in the U.S. have largely struggled to differentiate themselves from a range of competitors. Discount retailing giants like Dollar General Corp. and Wal-Mart have gobbled up a huge share of grocery sales in recent years--though Wal-Mart's business more recently has suffered. Whole Foods Stores Inc. and its imitators lure high-spending consumers. And Kroger, the biggest supermarket operator, has thrived using a strategy that offers both lower-price items and more gourmet fare.

The environment has spawned several big deals. Supervalu Inc. sold hundreds of Jewel-Osco and Albertsons stores to the private equity group that later bought Safeway Inc. And Harris Teeter Inc., a high-end chain based on the East Coast, agreed to be bought by Kroger in 2013.

"Ahold and Delhaize must merge to maintain competitive and operational retail relevance and long-term viability versus well-capitalized, highly capable competitors," said Burt Flickinger, a retail consultant at Strategic Resource Group.

Shares in the European companies had soared on deal speculation Monday, with Delhaize up 14.5% and Ahold up 5.5%. Shares in both edged up again by more than 1% on Tuesday.

The companies said their talks are preliminary and might not yield a deal.

While Ahold and Delhaize generally have limited overlap, antitrust concerns in some parts of the U.S. could be a hitch, analysts said. Ahold and Delhaize together would have 500 stores in North Carolina and 129 stores in New York, according to Exane BNP Paribas.

Competition concerns have been an issue in other food-related deals recently, including Family Dollar Stores Inc.'s decision earlier this year to merge with Dollar Tree Inc. rather than Dollar General.

Mr. Flickinger said Ahold and Delhaize could have a good chance for regulatory approval if they take the time to structure the deal correctly.

Ahold and Delhaize have been thinking about a combination for years, reportedly having held talks in 2006, as they seek greater scale and cost savings to take on the competition.

"The big obvious benefit, especially in the U.S., is the scale advantage the combined group will have in terms of purchasing power," said Pradeep Pratti, an analyst at Citi.

David Donnan, food and beverage consultant at A.T. Kearney, said acquisitions offer one of the few paths to significant expansion in the U.S., where most major local markets already are saturated with grocery stores. A merger also allows chains to leverage combined warehousing, technology and other back-office operations and save money.

But chains have to be careful not to lose the local dynamic that makes shoppers loyal. "Otherwise, the risk is that you get so efficient that you lose that focus on local consumers and that is critical to being competitive," Mr. Donnan said.

Still, some analysts were skeptical.

"Cost savings in retail acquisitions or mergers are highest when there is a large overlap and local scale economics improve," analysts at Bernstein said in a note on Monday. "In this case there is very limited local overlap.... We think this is a bad deal for Ahold investors."

Maarten van Tartwijk contributed to this article.

Write to Peter Evans at peter.evans@wsj.com

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