The Smithsonian Institution yesterday announced a donation of 1,000 masterworks of Asiatic art valued at more than $50 million for its proposed new center for oriental art.

The donor is Dr. Arthur M. Sackler, a New York research psychiatrist and medical publisher who owns one of the largest private collections of Chinese and Near Eastern art in existence. Yesterday's announcement confirmed an earlier report of a major Sackler donation.

Under terms of the agreement reached in July, the new museum will be named the Arthur M. Sackler Gallery. It is one of two museums proposed for a site along Independence Avenue bordered by the Freer Gallery of Art, the original Smithsonian building (the "castle") and the Arts and Industries Building. The other museum will house the National Museum of African Art.

In addition to the art donation, Sackler has agreed to contribute $4 million for construction of the new complex, which will cost about $75 million. According to Smithsonian assistant secretary Charles Blitzer, the only contingency in the agreement is that "we get the museum built."

The new complex will be financed by federal funds and private contributions. Although Congress has authorized $36.5 million for the two museums, it has not yet appropriated the money. A request for such an appropriation is included in the administration's budget for fiscal year 1983. Sackler's $4 million pledge, added to previous donations, means the Smithsonian has attained two-thirds of its goal for private funding, Blitzer said.

Smithsonian secretary S. Dillon Ripley called Sackler's donation of art "a truly magnificent gift" that will be "an incomparable highlight among the Smithsonian's Asian art holdings." Sackler praised Ripley's "brilliant planning and bold initiatives."

Sackler's entire collection of Asiatic art is believed to total more than 5,000 objects. The 1,000 items donated to the Smithsonian were selected by Dr. Thomas Lawton, director of the Freer Gallery, and curators at the Freer. Lawton is slated to become director of the new oriental art institution while retaining his post at the Freer.

Included in the gift are 475 Chinese jades dating from neolithic times (5000-1500 B.C.) to the 20th century, 150 Chinese bronzes from the Shang through the Han dynasties (circa 1523 B.C. to 220 A.D.), 68 Chinese paintings from as early as 960 A.D. to the 20th century, a large and varied group of Near Eastern objects including metalwork and sculpture from India, Cambodia, Thailand and Iran, and numerous examples of Chinese lacquer.

These objects will complement the Freer's superb holdings in many ways. For instance, the bronzes in Sackler's collection will vastly expand the range of styles represented in Smithsonian collections, according to Lawton. "Bronzes in the Freer collection come mainly from the great urban centers of Chinese civilization," he said, "while those we selected from Sackler's collection represent a wide range of provincial styles that archeologists and scholars are only now beginning to appreciate.

"The largeness of the collection gives it the breadth that is essential for the study of the cultures themselves," Lawton commented. The addition of the Sackler objects will make the new museum and study center "the important place in the world for people interested in Asian art," he said.

Objects in the Sackler gift will make up the entire opening exhibition of the new Sackler Gallery. "We hope to put every single one of them on display," Lawton said. Plans for the new gallery include approximately 26,000 square feet for exhibitions. The Freer contains about 20,000 square feet of exhibition space.

The Freer collection currently numbers about 12,000 objects, including some 9,000 objects included in the original gift from Detroit financier Charles Lang Freer. Only 8 percent of the collection is on view at any one time under the gallery's policy of rotating shows of its permanent holdings.

Although the Freer and Sackler collections will be united in administration, the collections will remain physically separated due to stipulations in Freer's bequest that prevent the gallery from loaning its works for exhibitions elsewhere or borrowing art works from other collections. No such restrictions are attached to the Sackler Gallery, so the new museum will be able to host major international shows of oriental and Near Eastern art.

Since it opened in 1922, the Freer has earned a worldwide reputation for the quality of its connoisseurship, research and publications. The addition of the Sackler Gallery and study center will enable the institutions to expand these activities, Lawton pointed out. A program of seminars and publications, based upon the Sackler collection and funded by the Arthur M. Sackler Foundation, will begin even before the new building is completed, he said.

Sackler, 69, is publisher of the International Medical Tribune Newspapers. The donation to the Smithsonian is the largest and most recent of his extensive list of philanthropies, which include support for the Arthur M. Sackler wing at the Metropolitan Museum of Art in New York (where much of his oriental collection has been in storage for years in the so-called "Sackler enclave"). He also endowed the Arthur M. Sackler Galleries at Princeton University, provided a science center at Clark University and, with his family, made possible two postgraduate biomedical institutions, one at Tufts University and the other at New York University.