SIMI VALLEY, Calif. (AP) _ Former President Reagan accepted a 3-ton chunk of the Berlin Wall on Thursday, saying the ''unnatural, ugly, unwelcome'' symbol will remind presidential library visitors of communist oppression.

''It shattered dreams and crushed hopes,'' Reagan told more than 1,000 guests gathered at the Ronald Reagan Presidential Library, which is still under construction, to witness the unveiling of the 9 1/2 -foot tall, 3 1/2 -feet wide concrete slab.

Moments after a white tarp was pulled away, revealing 1960s-style graffiti of a brilliantly-colored butterfly and flower design, Reagan and his wife, Nancy, walked up to the wall and touched it.

Thirty-four months earlier, on June 12, 1987, the nation's 40th president stood at the Berlin Wall's Brandenberg Gate and challenged Soviet leader Mikhail Gorbachev: ''Mr. Gorbachev, tear down this wall 3/8''

''For more than 28 years, the Berlin Wall stood as an unnatural, ugly, unwelcome, undeniable symbol of the oppression of communism,'' Reagan told guests, mostly GOP faithful and contributors to the $40 million library.

''It stood as a grim reminder of what happens when dictators strip the people of their freedom,'' he said in a six-minute speech.

On hand for the presentation were Leopold Siefker, the West German consul general in Los Angeles, and Norbert Reemer, minister counselor for the German Democratic Republic.

The chunk to be installed in the library was supplied by the Berlin Wall Commemorative Group, an East German organization.

During the 38-minute ceremony the UCLA marching band played tunes such as ''Surf City'' and ''Tequila,'' and the Bavarian Beer Garden Band played accordion ditties.

Guests included Lew Wasserman, the MCA Inc. chairman who was Reagan's Hollywood agent during his movie days, former U.S. Information Agency Charles Wick and fast food burger magnate Carl Karcher. Mel Torme sang the national anthem.

The 153,000-square-foot presidential library 40 miles northwest of Los Angeles is carved into a Ventura County hilltop. The concrete and steel superstructure overlooking green grass hills and beyond to the Pacific Ocean is due for completion Feb. 6, Reagan's 80th birthday.