The Fed announced in 2012 that it would begin a new programme of unlimited purchases of mortgage-backed securities – nicknamed QE3 or quantitative easing three. 
The first round of QE came during the financial crisis in 2008 and 2009. The second round (QE2), preceded by three months of fevered speculation, came in November 2010. 
Unlike previous programmes, the Fed’s third round of quantitative easing does not have a defined limit and will continue until the labour market improves.
Combined with its purchases of long-dated Treasuries under “Operation Twist”, this will see the Fed buying a total of $85bn of assets a month for the rest of 2012, similar to its QE2 programme in 2010. 
Operation Twist – the Fed’s programme of switching its short-term assets into longer-dated Treasuries in a QE-like effort to drive down long-term interest rates – should be complete by the end of 2012. 
In 2012, Guido Mantega, Brazil’s finance minister, has warned that the US Federal Reserve’s “protectionist” move to roll out more quantitative easing will reignite the currency wars with potentially drastic consequences for the rest of the world.
The Fed’s QE3 programme would “only have a marginal benefit [in the US] as there is already no lack of liquidity . . . and that liquidity is not going into production,” explained Mr Mantega.
He said it was instead depressing the dollar and aimed at boosting US exports.
Mr Mantega coined the phrase currency wars two years ago when the second round of QE by the Fed pushed a wall of money abroad, leading to a punishing appreciation of many emerging market currencies, especially Brazil’s.