MEXICO GETS consistent and steadfast support from the International Monetary Fund. Argentina does not. Mexico has just reached agreement with the IMF on the next stage of economic adjustment to manage its foreign debts. But IMF loans have now ceased to flow to Argentina until at least summer, when resumption will be contingent on better progress by the government in bringing the country's accounts into balance.

Mexico has put itself through a time of severe austerity that is now beginning to produce highly hopeful results. The country is moving back toward normal financial relations with the rest of the world, and the economy is beginning to grow vigorously again. But Argentina has never quite come to terms with the need to bring its accounts into better balance. One reliable indicator of the slippage is its inflation rate, now around 800 percent a year and rising.

The difference between the two countries' performance has less to do with technical economics than with their politics. Mexico is under a strong and self-confident government. Argentina is led by a promising but sometimes uncertain administration that is trying to pull together a deeply divided people. There are not many countries in which the various classes and interests have fought as vehemently, or as destructively, over the past generation for their respective shares of the national income. Labor, industry and the country's swollen military establishment have all been dangerously successful in pressing their claims over the years, with the result that all of those claims add up to substantially more than the country produces. Inflation is the classic result.

It's the government's job to work out the compromises that will allow the country to live within its means. President Raul Alfonsin evidently feels that, for political reasons, he cannot safely go much further to reduce incomes and consumption. But the IMF is telling him that he's got to go a lot further. Argentines point out that their present government is democratically elected, and does not rule by force like the military junta that preceded it. The IMF replies, correctly, that if it cannot get that inflation rate under control the dangers to Argentine democracy will inevitably increase anyway. The Argentines argue that conventional methods of reducing inflation are very hard on the poor. The answer is that the rest of the country -- the middle classes, business and especially the military -- can properly be asked to share the costs. But that idea is no more popular in Argentina than in the United States.

Mexico and Argentina got into financial trouble much the same way. The Argentine example shows the immense strains on a country as it tries to work its way out of that trouble. The Mexican example shows that the feat is possible.