The chairman of the Ford Motor Co. today endorsed Democratic legislation to slap a retaliatory tariff on imports from Japan and other countries if they do not open their markets to American products.

Donald E. Petersen, the Ford chairman, told the Midwest Governors Conference here that threats of retaliation are "about the only language the Japanese will respect."

Petersen called the Reagan administration's record on trade issues "appalling," and said that he and other business executives have no confidence that the president's new special trade representative, Clayton Yeutter, would battle for American interests against the Japanese and others.

Petersen drew a sympathetic response from the governors as he argued that "the trade situation is a national crisis, and here in the Midwest it hits us doubly hard, striking at the two most important sectors of our regional economy: agriculture and manufacturing."

None of the three Republicans present -- the governors of Indiana, Iowa and Missouri -- spoke up in defense of the administration, and the Democrats encouraged Petersen to pour on the criticism.

After saying it was "appalling" that the Reagan administration has "ignored" the report of the president's own commission on industrial competitiveness, Petersen said he has concluded that Congress now must act.

The bill he endorsed was introduced last month by Sen. Lloyd M. Bentsen Jr. (D-Tex.), a senior member of the Senate Finance Committee, and two key members of the House Ways and Means Committee, Chairman Dan Rostenkowski (D-Ill.) and Rep. Richard Gephardt (D-Mo.), who also is chairman of the House Democratic caucus.

It would impose a 25 percent tariff on goods from Japan and seven other countries, unless those countries took steps to reduce the current trade imbalance with the United States.

Petersen was particularly critical of Yeutter. He told the governors that at a meeting of the U.S.-Japan Business Council in Minneapolis last month, the Americans were making real progress toward convincing the Japanese that a trade crisis would erupt unless Japan acted promptly to open its markets -- and then Yeutter came in to deliver a speech.

"He didn't even refer to the problem," Petersen said, "and you could just see the Japanese relax."

The Ford executive said it was a "tragedy" that Bill Brock was removed from the trade representative post to become secretary of Labor. He praised Commerce Secretary Malcolm Baldrige's efforts with the Japanese but said Baldrige "is a very frustrated individual" because of the White House.

A spokeswoman for Yeutter said he would not comment on Peterson's remarks until he had seen a text.