NEW YORK — Walgreen Co., the largest U.S. drugstore chain, offered to buy Longs Drug Stores Corp. for $3 billion in an attempt to scuttle CVS Caremark Corp.'s agreement to acquire the California retailer.

Walgreen's $75-a-share cash offer is $3.50 — or 4.9 percent — higher per share than CVS/Caremark's agreement last month to buy Walnut Creek, Calif.-based Longs, Walgreen said in a statement yesterday.

Walgreen's offer, exactly one month after CVS' offer was made public, puts pressure on CVS to raise its bid or risk losing a chance to add pharmacies in two of the fastest-growing U.S. states, Nevada and Arizona. CVS also would acquire its first stores in Hawai'i, where Walgreen recently began expanding in competition with Longs.

CVS Chief Executive Officer Tom Ryan said yesterday on CNBC that the company is "not moving" on its price.

"Walgreen has had long-standing, sincere interest in Longs," Walgreen CEO Jeffrey Rein said in a letter to the Longs board.

If Walgreen ends up winning the contest for Longs, it would erase Walgreen's original intention of competing head to head in Hawai'i by opening as many of its stores next to Longs stores as possible.

Walgreen opened its first Hawai'i store last November on Ke'eaumoku Street. It expects to open two more stores in Kane'ohe and Kailua in late November or early December, followed by two more stores early next year in Kalihi and Lahaina, Maui. The company's long-term plan is to open 30 to 40 stores statewide.

Another possible effect of Walgreen acquiring Longs could be the end of the Longs brand in Hawai'i, if Walgreen decides to convert Longs stores to Walgreen stores.

CVS previously said it will maintain the Longs name in Hawai'i, but would convert all Longs stores on the Mainland to CVS. Longs operates about 520 stores in four states, including 39 in Hawai'i.

The Walgreen offer follows calls from investors urging Longs to seek a higher offer. Advisory Research Inc., Longs' biggest shareholder, said yesterday it wouldn't tender shares to CVS because its offer wasn't enough. That followed a similar statement from Pershing Square Capital Management LP, the hedge fund run by William Ackman. Ackman has said Longs' real estate is worth about as much as the CVS offer.

He would not comment on Walgreen's bid.

The Walgreen announcement was made after the stock market closed. Shares of Longs Drug Stores soared to $74.50 in after-hours trading after finishing the regular session down 7 cents at $71.66.

Deerfield, Ill.-based Walgreen said it is working with Lubert-Adler Management Co. and Klaff Realty LP to "address any potential store sales in connection with the transaction."

Goldman, Sachs & Co. is giving Walgreen financial advice, and Weil, Gotshal and Manges LLP is serving as its legal adviser.