Because of drought and other problems, Mexico is asking the United States to speed the provision of half a billion dollars in agricultural commodity credits. Two weeks ago, Mexico sent a signal to the world that it was dealing more effectively with its huge foreign-debt problem than many realized. It delayed drawing on a $1.1 billion second installment of a loan worked out with the International Monetary Fund (IMF).
Mexico's latest signal seems to say: ''We're doing a lot better than many realized, but we still have a long, long way to go.''
John A. Gavin, the American ambassador to Mexico, is in Washington, helping, among other things, to arrange for a speedup in the already promised half-billion dollars in credits. In an interview, Mr. Gavin said that he had asked President Reagan for his support, and that Mr. Reagan ''listened sympathetically.''
''He feels it is important we be forthcoming,'' said Gavin.
Reagan has yet to give final approval for the credit speedup. The Office of Management and Budget still has to make its determination on the matter.
The original plan was for Mexico to get the $500 million in credits for food, grains, and oilseed in the last quarter of this year, starting Oct. 1. The $500 million is part of $1.7 billion being provided under concessionary (favorable) terms. If the new Mexican request is agreed to, the credits could be provided within a matter of days.
''They need the grains,'' said Gavin. ''They need the foodstuffs. . . . There's been a great drought. Production has not been sufficient to feed what is still a burgeoning population.''
Gavin is also in Washington to help prepare for Reagan's first meeting with Mexico's President Miguel de la Madrid Hurtado since Mr. de la Madrid took office in December. The two leaders are to meet in mid-August at La Paz, Mexico, to discuss a wide range of issues, including the debt problem, trade, and Central America. Gavin hopes that such meetings between the American and Mexican leaders can become more frequent.
The ambassador described relations between Washington and Mexico, the US's third-largest trading partner, as healthy. But he acknowledged that the two countries have some differences, including ''certain differences of understanding'' on Central America.