Japan's steel exporters counterattacked their American competitors yesterday, urging the U.S. government to reject a complaint that they diverted steel shipments here as a result of agreements that set prices and limited exports of Japanese steel to the European Community.

In a petition filed with the office of the U.S. Trade Representative, the Japan Iron & Steel Exporters Association characterized the charges by the American steel industry as "without merit" factually and legally, and said a "virtually identical" complaint was found "groundless" by the U.S. government five years ago.

Furthermore, the Japanese exporters blamed "the relatively poor competitive position of the American steel industry" for its economic plight. American steel companies operated at about 40 percent of capacity last year with an unemployment rate of about 50 percent and a loss of almost 100,000 jobs.

"The U.S. steel industry has filed this petition during a period of unprecedented decline in demand for steel products," the Japanese counter petition stated.

"That decline is obviously not the result of any bilateral agreement or arrangement between the Japanese government and any of its trading partners. It is rather the result of a worldwide economic recession which has affected the vitality of the steel industries in all the major producing nations."

Moreover, the Japanese said, the conditions that led to the dismissal of the American complaint in 1978, when Japanese steel exports to the United States were at a historic high, are even more pronounced now because of a vastly lowered level of Japanese steel sales here because of the recession.

The Japanese steel exporters said their sales to the United States had remained steady at about 6 million tons since 1972 with the exceptions of 1976 and 1977, when it reached close to 8 million tons, and last year when it hit a new low of about 5 million tons.

The U.S. Trade Representative's office in the White House has until Jan. 31 to decide whether to accept the complaint, filed Dec. 16, in which the American Iron and Steel Institute and eight American steel makers asked the Reagan administration to restrict imports and set tariffs on Japanese steel.

Asked if he felt Japan was being made "a scapegoat" or "whipping boy" for the economic plight of the American steel industry, Japan Steel Information Center Chairman Seiichi Muto replied, "of course."

"We are not very happy," added Muto, president of NKK American Inc.

He said it was only coincidence that the Japanese steel exporters filed their petition the day Prime Minister Yasuhiro Nakasone left for Tokyo after a three-day visit here dominated by high level talks over the increasing trade tensions between the United States and Japan.

The Japanese acknowledged that their government has concluded agreements voluntarily restraining exports of steel to the European Community, but they said these are legal under international trade laws and similar to an agreement setting quotas on exports from Japan to the United States that was in effect between 1969 and 1974.

"The Japanese-EC agreements are neither intended to control nor do they control third-country markets including the U.S.," the Japanese said. "During the entire 1978-1982 period," the petition continued, "no diversion of Japanese exports to the U.S. markets occurred."

The Japanese also denied American steel industry charges that Japan and the European Community through a secret agreement had carved up the world markets into spheres of influence, with the European controlling the area west of Suez and the Japanese controlling the Far East coastal markets, India and Pakistan.

The American steel makers supplied the Office of the U.S. Trade Representative with minutes of meetings and communications between the Japanese and Europeans which they said backed their charges. But this documentation was labeled confidential and not released to the public despite statements that it would be. Steel industry representatives said the source of the documents could be traced if they were released publicly.