The march, on Mexican revolutionary Emiliano Zapata's birthday, was a show of force for the "old Mexico," opposed to the new, entrepreneurial nation that the businessman Fox has promised.

The protesters' rhetoric harkened back to Zapata's 1910-1917 revolution, which created the communal farms that served as the political backbone of the former ruling party, whose 71-year reign Fox ended in last year's elections.

Young and old marched in a sea of straw hats and baseball caps, cowboy boots and dusty tennis shoes. Families with small children armed with toy noisemakers joined men and women waving banners reading "United States out" and "Fox means misery."

"Fox sees the values of the revolution as history, the past," said Constantino Canstaneda, a 36-year-old tomato farmer who took a 10-hour bus ride from central Zacatecas state to participate in the protest.

"But I see the revolution in the land I work every day and in the faces of my children who will grow up to be farmers and have even less than I have now."

Streams of farmers chanted, "Long live Zapata! The struggle continues!" as they fanned out across the world's second-largest city to blockade government offices and shut down a half-dozen major boulevards.

"Rural Mexico could explode," said protest organizer Alvaro Lopez Rios, leader of the Agrarian Congress farm group. "This could take us to the edge of anarchy."

March organizers said more than 5,000 farmers participated, but Wednesday's turnout was lower than the tens of thousands promised by labor unions.

A number of separate marches cut slow, disorganized paces through the city and, as the day wore on, some protesters used their banners to shield themselves from the unrelenting afternoon sun.

The farmers are suffering from a prolonged drought that has withered crops in northern Mexico and low prices for coffee, basic grains, sugar and tropical cash crops like bananas.

They complained that Fox has abandoned any pretense at making Mexico self-sufficient in food production, something to which the former ruling party at least paid lip service -- largely to ensure farmers' political support.

Fox drew the battle lines sharply Tuesday, when he encouraged farmers to modernize, adopt new crops and rely less on government. He said he wanted to end "corruption, paternalism, political favoritism and bureaucracy" in farm policy.

But he showed no sign of stepping away from the two things that angered protesters most: his commitment to free-trade agreements that have let in cheap foreign grain and his close relationship with the United States.

"The United States and Canada protect their farmers with tariffs and subsidies," Martin Altorre, a 51-year-old banana and sugar cane farmer from southern Morelos state, said at a protest at Mexico City's Revolution monument.

"In Mexico, the farmers are getting hit hard, and Fox likes that."

Fox said Mexico doesn't have the money to compete in a subsidy race with developed countries and that farmers should leave behind corn and change to crops where they have an advantage -- like the winter-vegetable exports that made Fox's family wealthy.