Brazilian authorities announced new steps Wednesday to curb the rise in the real, with the currency riding a 12-year high against the US dollar.
The tax on financial transactions, a move aimed at curbing speculative inflows, will be boosted to a maximum of 25 percent under the new regulations.
The move is aimed at giving "security and stability to the market," Finance Minister Guido Mantega said.
"I think that with this move, speculation will be less profitable, and I think this will bring down the real," he added.
The move appeared to have an impact on Wednesday, with the dollar gaining 1.5 percent to a rate of 1.56 reals.
Brazil, which has one of the world's fastest-growing economies, is worried that the rising real will dent economic activity by making its exports more expensive. But the central bank's base rate of 12.5 percent has attracted huge amounts of capital.
The real has appreciated more than eight percent against the dollar since the start of the year.
Brazil's central bank spent about $36 billion intervening in the markets in an effort to slow the rise of the real in the first six months of the year.
Brazilian officials have criticized the United States for flooding the world with cheapening dollars and China for not floating its currency.