Secretary of State Alexander M. Haig Jr. and the foreign ministers of 21 other nations avoided confrontations and specifics as they made a new start here today on the stymied dialogue of developed and developing nations.

Haig and the others, representing some of the world's richest countries as well as some of the poorer, began planning for the "North-South summit" that will bring their national leaders here Oct. 22-23 to discuss the woes and inequities of the global economy.

The U.S. secretary of state called today's opening session "an extremely auspicious and promising start." He reported that a consensus is forming that the October summit, in line with U.S. wishes, will "avoid specific agendas" and forego "the burden" of a formal communique but will center instead on "free and open discussion" by President Reagan and the other heads of state.

The reagan administration has little sympathy with the previous rhetoric of the North-South dialogue, which Haig has called "both confrontational and sterile," and in this connection is unhappy with the drive for "global negotiations" between North and South sponsored by a large bloc of developing countries.

A central aim of U.S. planning for the October summit is to avoid placing Reagan under pressure to agree to specific proposals or pledges arising from the grievances of developing nations about the workings of the global economy.

In keeping with previous tentative agreements and U.S. wishes, today's consensus rejected a plea by French Foreign Minister Claude Cheysson that advance papers be drafted on the issues to be covered in October to provide a greater opportunity for the leaders to deal with specifics.

According to conference sources, the majority of those present, including the foreign ministers of India, Brazil and China, disagreed with Cheysson's idea.

The conference cochairman, Foreign Minister Jorge Castaneda of Mexico, told reporters the ministers sought to avoid confrontation here and at the October summit.

Nonetheless, officials from developing countries, notably Brazilian Foreign Minister Ramiro Elysio Saraiva Guerreiro, spoke bluntly of the worsened condition of the world economy and the need for international action.

Guerreiro, in a speech to the private meeting later released by his delegation, said it is essential that the October summit provide "conclusions" and "concrete expressions" to implement "a political consensus on the urgent need for action" regarding North-South issues.

Saying that the world economy is suffering from "a profound structural crisis," the representative of debt-ridden Brazil said he has no confidence in the ability of market forces to deal with the situation automatically. "The problems that we face require political solutions . . . concerted actions of the governments to correct inequalities which warp the world economy," he said.

Despite the U.S. attitude, today's discussions provided new evidence of support, at least on the rhetorical level, for the "global negotiations" idea.According to a diplomat present, every foreign minister except Haig stated support for going ahead with such deliberations under the sponsorship of the United Nations.

Even Saudi Arabia's foreign minister, Prince Saud, whose oil-rich country has been cool in the past to the idea, supported it today, the diplomat said.

Asked about the U.S. view, Haig said, "The topic of global negotiations is best dealt with in a global organization. This is not a global organization."

The summit that the meetings today and Sunday are preparing was called by Mexico following recommendations from a private international commission headed by the former West German chancellor, Willy Brandt.