The decision by the new Argentine government to tax speculative capital that stays in the country less than 180 days, introduces a new element that could begin to shape the new MERCOSUR originally proposed by Brazil. Despite declaring a moratorium on the payment of its debts, Argentina has been considered a favourable deposit for capital, due to the very low interest rates in the principal capitalist countries, starting with the United States. This keeps the value of the Peso under control, reduces the exporting capacity of the country and affects its balance of payments, thus explaining the decision made by the President of Argentina. Similar measures existed in Chile before the Brazilian crisis of 1999, however, they had to be suspended because neighbouring countries were turning in the opposite direction and creating increasing opportunities to deposit financial capital. Measures of this nature are not feasible if neighbouring countries maintain high interest rates without any form of taxation. The measures employed by the Argentine government have presented Brazil with the challenge of either adopting similar measures or of abandoning the project of constructing a stronger MERCOSUR, which includes a Parliament and common currency. Without coordinating their foreign exchange policies, they will make little or no progress. Nevertheless, at this point in time, at the end of the first semester of the new government, Brazil is assuming a liberal stance in the face of the change in policy and there is nothing to suggest that Brazil will follow Argentina for the moment. Even so, not following Argentina, despite declaring support for Kirchner's measures, will in reality be sabotage, because of the current high interest rates – higher than two months ago – and because of the Brazilian government's disposition to continue to attract speculative capital. The situation is presenting MERCOSUR with an unexpected challenge of having to comment on a matter that is currently dividing the block. What could transform the situation is a change in direction of the economic policy of Lula's government, in the announced transition to the policy's second phase. In such an event, the stimulus to development would be coupled with a disincentive to speculative capital. However, by then Lula's government will have to abandon its current plan to reintroduce development in the framework of microeconomic policies, without shaking the pillars of macroeconomic policy. Not doing so will, in practice, imply making the Argentine measures unfeasible and opening a divide between the two main members of MERCOSUR. (Translation by ALAI)