LOS ANGELES, APRIL 6 -- A new study, issued in the midst of a debate over foreign control of the American economy, reported today that Japanese investment in U.S. real estate jumped 70 percent in 1987 to a record $12.77 billion.

The study by the accounting firm of Kenneth Leventhal & Co. said the new Japanese investments were concentrated in Hawaii, California and New York, but also were noticeable in Arizona, Illinois, Texas, Washington state, Florida, Massachusetts and the District of Columbia.

Some experts said the figures indicate that the Japanese are now the largest foreign holders of American land and buildings. The study estimated total Japanese ownership of U.S. real estate at $26.34 billion and predicted that another $16 billion to $19 billion in purchases would be made this year.

The report, released during a conference sponsored by the University of Southern California's Lusk Center for Real Estate Development, arrived as Congress and the White House remained embroiled in a dispute over disclosure of foreign ownership of property in the United States.

An amendment to the comprehensive trade bill agreed upon last week by House and Senate conferees would require that major foreign investors register with the U.S. government.

The amendment, proposed by Rep. John Bryant (D-Tex.), is opposed by the Reagan administration,

"This is the most dramatic thing that is occurring in the American economy," said Bryant press secretary Carlton Carl.

"Foreign ownership of American assets has tripled in the last seven years, and basically we don't know who is involved here ... and how much influence they have over the American economy," Carl said.

A White House spokesman said the Bryant amendment would have a "chilling effect" on healthy investment in the United States.

Robert Lawrence, an economist and senior fellow at the Brookings Institution, said that although Japanese and other foreign direct investment has increased, it still equaled only the amount of direct American investment abroad. Attempts to control foreign investment here, he said, would make American investors "very vulnerable to retaliation from foreign countries."

Foreign purchase of U.S. real estate, Lawrence added, is the least likely to harm the American economy because "it is an asset you can't take away with you."

Jack R. Rodman, managing partner of Leventhal's office here, said the new Japanese investors were "buoyed by the increased value of the yen, lack of alternative real estate investments within their own country, and overflowing cash reserves from the balance of payments surplus."

Rodman said his firm's study may have underestimated the total Japanese investment because it did not record all real estate transactions or the property component of other large Japanese investments such as the $2 billion purchase of the CBS Records Group by Sony Corp.

Office properties are still the favorite Japanese investment, the study said, but many Japanese businessmen are now moving into American hotel and resort properties -- a 160 percent increase in last year alone.

Hawaii saw the largest total of new Japanese property purchases in 1987, $3.3 billion, followed by $2.98 billion in California and $2.34 billion in New York. The three states took 76 percent of all new Japanese investments.

The study estimated that Japanese investors own a total of $510 million in District property.

The study said Japanese property investment jumped twentyfold in some cities in which Japanese investors had previously shown little interest, particularly Phoenix, Chicago, Dallas, Miami and Seattle. Rodman said this activity grew in part from limited partnerships offered by U.S. insurance companies to smaller institutional investors in Japan.

Rodman said the study indicates growing Japanese interest in suburban properties, including single-family homes, condominiums and apartments.

Japanese investments rose from $1.86 billion in 1985 to $7.53 billion in 1986 to $12.77 billion last year, the study said.

The figures were compiled from Leventhal's Japanese Data Base, which tracks investment by type of product, location, size, value and some other measures.