BUENOS AIRES Developed nations should expect a fight if they insist on subsidies that undermine South America's agriculture, Mercosur ministers said Saturday.

"We will go to the World Trade Organization," said Brazil's Agriculture Minister Marcus Pratini de Moraes.

"We won't import subsidized products," he said.

Mercosur's agriculture ministers stayed on after Friday's half-day summit of Brazilian, Paraguayan, Uruguayan and Argentine presidents who invited Mexican President Vicente Fox to join them in discussion of admitting Mexico to the free-trade zone, AFP reported.

"Weakening our economies" reduces "our ability to pay" our debts, said Rafael Delpech, agriculture minister of Argentina. Gonzalo Gonzalez of Uruguay called Mercosur, which includes most of South American's economy, "the last, best food reserve on the planet and we have to make our worth felt." Walter Nunez Rodriguez of Bolivia said Europe and the United States were "exercising an illicit trade policy."

"With the equivalent of three months' worth of the subsidies that they provide -- some $90 billion -- they could resolve hunger and poverty all over the world," he said.