Emerging market giants Brazil and China on Tuesday agreed to exchange up to $30 billion of each other's currency, in a bid to lessen the impact of financial crises.
Brazilian Central Bank Governor Alexandre Tombini said the agreement would be useful "in the case of turbulence in financial markets."
The funds could be used to back trade even if dollars became difficult to source in the event of a crisis like the 2008 banking meltdown.
The cash could be used to provide credit for trade.
The initiative was tentatively agreed last June and was signed on the sidelines of a summit of BRICS leaders in Durban.