TOKYO, JULY 2 -- The Japanese government said today it wouldn't interfere with a proposed U.S. import ban on Toshiba Corp. stemming from that company's sale of sensitive technology to the Soviet Union.

Japanese officials also vowed to take steps to prevent any further violations of rules controlling exports to communist countries.

The U.S. Senate voted Tuesday in favor of banning Toshiba and a Norwegian company, Kongsberg Vaapenfabrikk, from selling their products in the United States for two to five years. The proposal still needs approval of the House and President Reagan to take effect.

Kongsberg and Toshiba Machine Co., a Toshiba subsidiary, sold the Soviet Union propeller-milling equipment that will allow Soviet submarines to run quietly and escape detection.

The president and chairman of Toshiba Corp. resigned Wednesday to take responsibility for the illegal sales, though both denied any direct link between the parent company and the transactions.

Four high-ranking executives of the subsidiary also have stepped down, while two others have been indicted on charges of violating Japan's decrees banning exports of 178 high-technology items to communist countries. The decrees are in line with rules of the Paris-based Coordinating Committee for Export Control (Cocom), which regulates exports to communist nations.

In a regular Foreign Ministry briefing today, Yukio Okamoto, director of the National Security Affairs Division, said "there is a very, very strong feeling and recognition" within the Japanese government that "we should never allow these things to happen again."

Okamoto added that the government does not intend to "protect Toshiba from American congressional action, although such harsh provisions deliberated in the American Congress are certainly not conducive" to U.S.-Japan relations.

In San Francisco, a Toshiba Corp. officials today warned that some employes working for the company in the United States could lose their jobs if a ban on Toshiba imports becomes law.

Takao Hayashida, vice president for Toshiba America, predicted the 4,000 people who work for Toshiba's U.S. subsidiary would be "quite seriously affected" by the proposed ban.

Toshiba Corp. had an estimated $4 billion in sales in the United States last year. Its products include semiconductors, color television sets, video recorders and personal computers.

It operates a semiconductor manufacturing plant in Sunnyvale, Calif.; a Lebanon, Tenn. plant that makes television sets and microwave ovens; a motor manufacturing plant in Houston and an Irvine, Calif., facility that makes communications and medical equipment.

Hayashida predicted that "if that ban was passed, about 10 percent of total sales of Toshiba Corp. will be lost." He said two of every 10 Toshiba products sold in the United States are produced in the United States, with the rest coming from Japan. In Tokyo, the minister of international trade and industry, Hajime Tamura, was quoted as expressing regret over the Senate action. He was speaking at an emergency meeting with leaders of top Japanese industrial associations.

Atsushi Iwaai, director of the strategic-export control office of the Ministry of International Trade and Industry (MITI), also quoted Tamura as saying export control violations "could seriously damage confidence not only in Japanese industry but also in Japan as a whole."

Iwaai, speaking at a news conference, said Tamura asked industrial leaders to ensure that they adhere to the rules of Cocom.

Masakazu Toyoda, director for international policy planning at MITI, said the Japanese government first became aware of Toshiba Machine's violation when it received an inquiry from the Cocom council in Paris in December 1985, followed by another from the U.S. Department of Defense in June 1986.

Toyoda said the ministry wasn't able to make a thorough investigation at the time because of a lack of evidence and "enough proof to make a charge against Toshiba Machine."

But in December 1986, another U.S. inquiry contained enough information for MITI to start a thorough investigation, he said.

Iwaai said MITI will increase the number of export license inspectors and strengthen inspection at custom clearance companies.