LOS ANGELES — With the Los Angeles County Museum of Art just weeks away from demolishing four buildings on its campus to make way for a $650 million structure by Peter Zumthor, the Ahmanson Foundation said Tuesday that it is suspending its decades-long program of buying art for the museum over concerns about the effects of the radical redesign.

In a telephone interview William Ahmanson, president of the foundation, said he fears that under the Zumthor plan — a sweeping, one-level structure designed to flatten the traditional museum hierarchies that privilege particular centuries and cultures — many European artworks his family’s foundation donated will end up in storage.

“It’s my understanding that LACMA is changing from an encyclopedic museum with a robust permanent collection to a museum with some permanent collection works on view and more temporary exhibitions,” Mr. Ahmanson, who remains a board member there, said. “The concern is that the carefully curated collection we’ve amassed over decades may never see the light of day again.”

The foundation’s decision was previously reported by The Los Angeles Times.

Starting in 1972, the Ahmanson Foundation has spent about $130 million to finance the museum’s acquisitions of 99 artworks, including masterpieces like “The Magdalen With the Smoking Flame” by Georges de La Tour, others by Rembrandt, Watteau and Bernini, and a suite of 42 French oil sketches. The donations were not made with any contractual stipulations that the works remain on view. But historically, Mr. Ahmanson said, “nearly all” of the works except for the light-sensitive French sketches have been on display at any given time.