A day after finance minister Guido Mantega pledged not to allow America to “melt the dollar”, Brazil’s central bank announced that domestic lenders would have higher reserve requirements against foreign exchange positions. The move is Brazil’s third since October aimed at discouraging “hot money” from chasing the real higher and so undermining the nation’s competitiveness in the face of a weak dollar.

The Brazilian currency, which is up more than 35pc against the dollar since early 2009, slipped 0.8pc in New York to R$1.6869. Brazil was the first country last year to highlight the dangers of “currency wars” and Mr Mantega made it clear on Wednesday that the nation was equally alive to the problem this year. “We’re not going to allow our American friends to melt the dollar,” he said, believing that the US’s $600bn (£388bn) injection into its economy was an unfair attempt to boost exports.

Brazil will force lenders to maintain the reserve deposits in cash – on which they will not earn interest. Aldo Mendes, the central bank’s director of monetary policy, said the new curbs had the potential to trim short positions in the dollar to $10bn from last month’s $16.8bn. Brazil’s move followed Chile’s intervention on Monday, with a plan to buy $12bn of US dollars to bolster the greenback against the peso. The Chilean peso has gained more than 17pc against the US dollar since June.