Latin American debtor nations, fearing a possible snub by the United States, have decided against unilaterally scheduling a conference with industrial nations in an effort to change the way the debtors repay their loans.

The United States has been firmly opposed to such a conference, which most Latin American nations feel is an imperative first step toward increasing aid from Western nations. Without increased help, they feel, the region will be unable to avoid an economic collapse because of its $360 billion debt burden.

Sources at the summit meeting here of Latin American foreign and finance ministers said the nations had toyed with the idea of scheduling such a conference but instead have decided to make a concerted diplomatic effort to change the Reagan administration's mind about the need both for a conference and for increased assistance.

These sources said the so-called Cartagena Group -- named for the Colombian resort where the first such summit took place last June -- will devise both an approach and a communique' aimed first at the interim meetings of the World Bank and International Monetary Fund in April and for the diplomatic campaign the Latin American debtor nations will undertake.

Britain also opposes special debt meetings, although sources said France and Japan have proved more receptive to treating the region's debts as a special problem that should be dealt with outside traditional forums such as the IMF.

Several deputy ministers who did the staff work early this week for the ministerial meeting that began today said that most of the difficulty the group faces in devising a common front is inexperience in doing things together.

"The debt crisis has done more for Latin American political integration than 150 years of rhetoric," said one deputy foreign minister. He said the nations still are learning the nuts and bolts of presenting a case they feel compelling rather than merely issuing high-sounding communique's.

There are, however, some differences among the debtor nations -- primarily among those that are coming out of their crisis and those that remain in severe economic straits.

Since the onset of the Latin American debt crisis in August 1982, the Reagan administration has argued that there could be no joint effort to resolve the debt dilemma because each country's problems were different and most of them were between the country itself and its bank lenders. Commercial banks hold about two-thirds of the region's debt.

U.S. officials also have said privately that any government effort would involve taxpayer money and that increased aid to the region would be impossible to push for, especially in an era in which the United States already is running a massive budget deficit.

But sources at the third meeting of the Cartagena Group said that their debt problem is so involved with economic policies over which they have no control -- primarily spending, monetary and trade policies in the United States -- that a political solution is required as well as a financial one.

They said that the U.S. government has been lulled into believing that the region's problems are receding because several of the biggest debtors -- primarily Mexico, Venezuela and Brazil -- appear to have made substantial progress in cutting their budget deficits, generating dollars they need to pay their debts and resuming economic growth.

But the sources noted that other debtor countries, such as Peru and Chile, remain on the brink of economic collapse. They added that Argentina's newly installed economic program is off to a shaky start and that the chances of it succeeding are problematic. In January, for example, Argentina's inflation rate soared to 24 percent, which works out to an annual rate of more than 1,200 percent.

The ministers are scheduled to reach an agreement and issue a communique' Friday. The communique' is expected, among other things, to ask the United States to take special efforts to reduce its budget deficit -- which the ministers see as the primary source of the high interest rates that make repaying their debts so burdensome.