Is a free-trade deal the best option for Brazil and China?

For Brazil and China, the 11th BRICS summit—held Wednesday and Thursday this week—had a special meaning. The event helped to put an end at the hard feelings caused by president Jair Bolsonaro’s rhetoric during the election campaign, when he declared that “the Chinese are trying to buy Brazil.” In a much friendlier business and political climate, the president himself spoke of strengthening Brazil’s ties with China, while Economy Minister Paulo Guedes was even more optimistic, considering a free-trade deal between the countries.

But how would such an arrangement work?

Technically, any negotiation for a free-trade deal—which is a comprehensive agreement that scraps tariffs for roughly 90 percent of products—would have to involve Mercosur, the South American trade bloc of which Brazil is a member. No Mercosur country can sign bilateral trade deals without the involvement of the rest of the bloc.

However, Mr. Guedes did not provide many details about the plan and it was unclear whether the negotiations involved Mercosur or not, during a speech at a New Development Bank (NDB) event in Brasília....