TOKYO (AP) _ Japanese auto industry officials today said it was unlikely they would sharply increase vehicle shipments to the United States next year, even if their government ends voluntary export quotas.

Shigehira Yoshioka, a spokesman for the Japan Automobile Manufacturer's Association, said any rush of exports could prompt U.S. retaliation, adding, ''Our industry thinks U.S.-Japan relations are very important since the U.S. market is so big.''

Since 1981, Japan agreed to progressively higher ceilings on its shipments to allow U.S. carmakers to adjust to fiercer foreign compeition. The limit for the fiscal 1985, which ends March 31, is 2.3 million vehicles.

But Japanese newspapers Friday quoted a top official of the Ministry of International Trade and Industry as saying an extension of the restraints is ''out of the question unless there is some exceptional'' justification.

The official quoted was not named, but a lower-ranking official of the ministry's automobile division who refused to be identified confirmed the statement.

The latest statement underlined MITI Minister Keijiro Murata's comments to a news conference last March 28, in which he said MITI would direct Japanese automakers to ''conduct exports with prudence'' during fiscal 1985.

He called the restraints a ''transitory'' measure to maintain the free trade system and avoid a sudden export surge. In response to a question, he said the policy ''in principle, is only for one year.''

Ministry officials, asking not to be identified, said Murata's comments meant the restraints would continue only through fiscal 1985, and there was no consideration being given to yet another extension.

Although Friday's statement on export restraints essentially restated the position made public last March, it triggered sharp reaction in Washington. Senate supporters of the U.S. auto industry lashed out at the Japanese for what one called ''national arrogance.''

However, in a telephone interview, Yoshioka said the Japanese industry ''does not believe a rush (of exports) will happen.''

A spokesman for Nissan Motor Co., one of Japan's largest automakers, also said in a telephone interview that the Japanese would not want to imperil their access to the U.S. market.

Nonetheless, the industry has not considered withholding shipments in 1986 and ''maintains a basic consensus that the restraints should be dropped,'' said Shigeru Sawada, Nissan's international public relations manager.

The spokesmen declined to speculate on how many automobiles Japan may ship to the United States after March.

''I can't comment on next year,'' Yoshioka said. ''But there are many political pressures ... (and) politicians say a smooth transition period is needed.''

Under U.S. pressure, the Japanese government initiated the so-called ''voluntary controls'' on auto exports in 1981 for a three-year period, setting the level at 1.63 million vehicles, to give the U.S. auto industry time to boost its competitiveness.

Japan extended the measure in 1984 but raised the ceiling to 1.85 million vehicles. In 1985, Japan set what it called an ''informal'' voluntary ceiling for U.S.-bound car exports, raising the level 24.3 percent above the 1984 ceiling.

Both U.S. and Japanese officials have estimated that without the restraints, Japanese imports this year would have topped 2.6 million vehicles - at least 300,000 more autos than allowed under the current limit. Japan currently holds 20 percent of the U.S. car market.

A U.S. Embassy official who spoke on condition of anonymity said the rising value of the yen and Japanese investment in the U.S. auto industry may have made the restraints ''meaningless.''

He said exports will decline naturally as a stronger yen raises prices of Japanese products and as five Japanese companies sell more automobiles from their U.S. plants.

U.S. auto companies joined Washington lawmakers in criticizing the planned end to restraints.

Ford Motor Co. said in a statement that after having boosted shipments to the United States by 24 percent this year, ''it's almost incredible that Japan would consider increasing the flood.''