TOKYO, AUG. 18 -- Japan and the United States today ended nearly a year of talks aimed at boosting Japanese purchases of U.S.-made auto parts, and the chief U.S. negotiator said the main result was to make companies on both sides realize the need to change their practices.

"The biggest thing we've done is heighten awareness, and I'm confident we did that," said C. Bruce Smart, U.S. undersecretary of Commerce for international trade.

Smart said that unlike earlier trade issues, the principal problem in auto parts was not government-imposed trade barriers but rather "attitudinal problems in companies both in Japan and the United States."

Japanese car manufacturers, he said, need to end their custom of buying only from traditional suppliers, while U.S. parts makers should learn how to compete "Japanese-style."

"We have pointed out to American suppliers the need to comply with the Japanese manufacturing system based on innovation in the design of parts, just-in-time delivery and 100 percent good quality," he said.

In their final report on the talks, the two sides said they agreed that the Japan Automobile Manufacturers Association would collect information on sales by U.S. parts suppliers to Japanese car makers, and would provide the names of buying agents at each Japanese vehicle maker to make it easier for U.S. companies interested in selling their products.

The two governments also agreed to boost automobile trade by cooperating in holding car shows and seminars, the report said. "Both governments recognize that a strong automotive industry in each of their countries is best fostered by relying on market forces in a competitive environment," it added.

The two sides said they would hold occasional meetings to review the progress of the agreement.

The automotive sector is the largest component of U.S.-Japan trade, and accounts for more than half the bilateral trade imbalance, Smart said.

Last year, the United States tallied a record $58.6 billion trade deficit with Japan, according to U.S. figures.

The Japanese manufacturer's association said Japanese car companies in Japan and their U.S. subsidiaries bought $2.5 billion in parts from 807 U.S. parts suppliers in fiscal 1986, which ended in March, compared with $1.7 billion the previous year.

But Smart said sales of U.S.-made parts to auto makers in Japan had not increased substantially, while sales to Japanese subsidiaries in the United States remained roughly proportional to their growing vehicle assembly capacity.

"Therefore, it is too early to say ... . whether we have accomplished our objectives," he said.

Honda Motor Co. announced earlier this week that it will increase its quota of imported auto parts by 20 percent this year to 40 billion yen, or $266 million, from 33.2 billion yen in 1986.

The Japanese auto maker said it wanted to help the auto parts negotiations, and also was responding to the rise of the Japanese yen, which has enhanced its buying power.

Smart said the outcome of the talks would have "relatively little positive effect" on the omnibus trade bill now in Congress, which both U.S. and Japanese government officials have labeled protectionist. "But if there had not been an acceptable outcome to the talks, it certainly would have been very harmful for the trade bill," he said.

{The leaders of a congressional task force on the issue attacked the agreement. Rep. Marcie Kaptur (D-Ohio) called it "another whopping failure of the Reagan administration in the area of trade" and said Japan has increased its U.S. sales while the talks were underway instead of buying more American-made products.

{Rep. Sander M. Levin (D-Mich.) said the "paltry results" of the Tokyo talks underscore the need for Congress to include in trade legislation "tools U.S. trade negotiators need to pry open protected markets like the Japanese auto parts sector."}

The negotiations on auto parts, which began in August 1986, are the fifth in a series of what are called market-oriented, sector-specific trade talks. Previous negotiations focused on pharmaceuticals, forestry products, electronics and telecommunications.