A leading Japanese industrialist and a former foreign minister, describing Japan as in the midst of a "historic change" from a society dominated by a need to export, pleaded here yesterday for patience from Americans who are growing increasingly frustrated by the one-way nature of trade between the countries.

"Looking from our side, we are making very serious efforts to change long-cherished, long-established rules" that have been used to restrict imports into Japan, said former foreign minister Saburo Okita.

He and Akio Morita, chairman of Sony Corp., are here as special emissaries of Prime Minister Yasohiro Nakasone to try to ease growing trade frictions between the two countries. Those frictions are fueled in part by Japan's $36.8 billion surplus last year and by the growing feeling that competitive U.S. products are kept out of Japanese markets. Okita is the chairman and Morita is a member of an advisory committee named by Nakasone to study market access.

Shortly after the two Japanese emissaries, at a meeting with reporters from The Washington Post, called for more time to make the transition from a nation dominated by a need to export to one willing to accept imports, officials of the American Electronics Association said their patience is growing thin.

The AEA representatives said at a press briefing that they feared regulations Japan is expected to issue May 1 will further restrict U.S. companies from that telecommunications market instead of opening it wider, as Nakasone and other Japanese officials have promised.

"There really is no more patience," said William K. Krist, director of international trade affairs for AEA. "Now is the time to get access in Japan. If we don't get it, we're going to have to rethink our whole free-trade approach.

"If I were Japan and didn't really move to assure an open-market system, I wouldn't be real sanguine" about future relations, he said.

The AEA representatives said they have not seen the Japanese regulations, but have heard reports that they contain complex certification procedures that in the past have been used to keep American products out.

"We are trying to make our market open in telecommunications," Morita said. "We are trying to get it open as soon as possible." He added that Japan's telecommunications market is dominated by companies close to Nippon Telegraph and Telephone, the former government monopoly. He said his company, Sony, welcomes the competition that an open policy will bring.

Okita and Morita said they recognized the new, charged atmosphere here over trade. "I feel this time it is very serious," Okita said. "I notice a big difference in the past two months or so."

One indication of this difference is that Sen. John C. Danforth (R-Mo.), chairman of the Senate Finance Committee's trade panel, refused to see them and told the Japanese embassy he will not be available to any delegations from Japan. Some U.S. trade officials have expressed their private support for Danforth's action.

"We are very much concerned about the situation here," Morita added. "All Japan, especially the private sector, is very sensitive to what is going on in Washington. That is why the private sector and also the government side are working very hard to take the necessary steps as fast as possible.

"But during the course of a transition, there are many problems," he added.

Both men expressed concern that Japan's trade surplus is growing so rapidly that increased U.S. sales are unlikely to make much of a difference. Moreover, "some of the expectations [in the United States] have gone too far," Okita said.

He said he feared the Japanese system can't move fast enough "to catch up with this change" that has given Japan a massive trade surplus with the United States. "The figure is getting too large in a very short period. Sometimes the political change can't catch up," he said in an apparent reference to groups in Japan who oppose the prime minister's market-opening moves.