Brazil is warning that the world is on course for a full-scale trade war because of what it calls currency manipulation by China, the United States and others.
Finance Minister Guido Mantega said Brazil was preparing moves to prevent further appreciation of its currency.
He said his government would raise the issue at the World Trade Organization and the G20 group of rich and developing countries.
"This is a currency war which is turning into a trade war," Mr Mantega told the Financial Times newspaper in his first major interview since President Dilma Rousseff took office on 1 January.
He said Brazil's trade with the US had slipped from an annual surplus of about $US15 billion to a deficit of $6 billion because of US efforts to revive its economy through loose monetary policy.
"The exchange rate is one of the main drivers of economic policy, more so even than productivity," he said.
Mr Mantega added that China's "undervalued currency" was also distorting world trade.
Mr Mantega has been finance minister since 2006. In September last year he accused some rich countries of deliberately devaluing their currencies to boost exports and make their economies more competitive.
The Brazilian real has increased by 39% against the US dollar in the last two years, as Brazil's economy has grown.
The BBC reports Brazil has been swamped by a flood of foreign capital that is taking advantage of low interest rates in the developed world to chase high returns in emerging economies.
The International Monetary Fund warned in October that some countries appeared to be trying to use their currencies "as a weapon" and the issue of currency manipulation was discussed at a summit of the G20 group in November.