The Reagan administration has informally conveyed to Japan through Ambassador Mike Mansfield that it expects Japan to voluntarily limit car exports to the U.S. to 1.6 million this calendar year, down from 1.9 million in 1980, and a least one part of the Japanese government seems ready to settle the issue at that figure.

White House sources said that the formal request for a sharp curtailment in Japanese car shipments to this country will be delivered next week, following Japanese Foreign Minister Masayoshi Ito's return to Tokyo and his report on conversations held here earlier this week.

At the same time, the Japanese Foreign Ministry, while conceding that Japan must "cooperate" with the Reagan administration to solve the auto crisis by holding back imports, is urging that as a condition for an agreement, the U.S. must admit that Japan is not to blame for the American industry's problems.

"Japan in the past has paid for its business successes by being treated as if it were a criminal," a high Japanese official said in an interview. "Now, we're willing to cooperate on autos, but we want them [the Americans] to agree that we're not to blame."

He indicated that it had become an issue involving national pride. Japanese leaders want the U.S. to drop what they consider to be an accusatory tone, and publicly recognize that the U.S. companies and unions have created most of the problem for themselves.

Reports from Tokyo yesterday indicated that the powerful Ministry of International Trade and Industry (MITI) decided to go along with a 1.6 million limit on this year's exports to the U.S. to calm protectionist sentiment here, but cautioned that the government would have to persuade recalcitrant auto producers to go along. There was at least some indication that Foreign Ministry officials were not yet ready to agree with the MITI position.

White House sources said Robert Hormats, Assistant Secretary of State-designate for Economic Affairs, will coordinate negotiations for the U.S. side, the result of Secretary of State Alexander Haig's successful claim of the lead role for his department. But administration officials also said that Trade Ambassador William Brock will play a role, benefitting from Haig's loss of face in an overall clash with the White House on foreign policy management.

A reduction in Japanese exports from 1.9 million last year to l.6 million this year would require a much deeper slash in present shipments, which have been at a rate exceeding 2.1 million, according to some American sources. But Japanese officials who had accompanied Foreign Minister Ito here claim that the first-quarter rate was only 1.8 million.

According to White House sources, Hormats will begin his negotiations with a starting figure of only 1.4 million for 1981.The President wants the U.S. team to be conciliatory, sources said, but is willing to use the threat of legialation incorporating mandatory restrictions as a "stick" to move the talks alone to a conclusion. A Japanese source in Washington said flatly that the issue "must be settled" before Prime Minister Suzuki arrives in Washington in May.

"It is simply unfair to blame Japan for this situation," said Taizo Watanabe, a spokesman for the Ministry of Foreign Affairs, who accompanied Ito here. "Japanese imports are not the cause of the American industry's problems, but the result of consumer preference for better-quality cars at a reasonable price."

He pointed out that in recent years Japan had been pressured to "cooperate" with the U.S. by limiting its exports of color televisions and steel products, after Japanese companies had been charged with pursuing unfair trade practices. But despite quotas and other measures designed to keep out Japanese products, he said, the results for the affected U.S. industries had been "dismal."

Watanabe said that the Japanese government recognizes that the auto industry is so important that the Reagan administration must make an effort to save it, but unless Japanese "cooperation" is part of a thorough revitalization program, "it will mean nothing."

He argued that the Reagan administration should not give in to the extreme protectionist demands of the U.S. companies, which have been willing to pay wages running 60 percent higher than the overall industrial average.