Group of Seven finance leaders will issue a statement stressing their readiness to take all necessary steps to calm markets if Britain votes to exit the European Union, government officials with direct knowledge of the preparations said on Thursday.
Finance authorities of the G7 advanced economies are negotiating a draft of the statement that would be issued shortly after Thursday's referendum results become clear, the officials said on condition of anonymity due to the sensitivity of the matter.
The statement will reconfirm an agreement among G7 nations that "excess volatility and disorderly currency moves are undesirable," one of the officials said.
Japanese Finance Minister Taro Aso may also issue a separate statement to aimed at preventing a Brexit vote from triggering excessive yen rises, the officials said.
Aso's statement would be similar to one the Ministry of Finance issued last year, when it said it would watch market moves carefully and work closely with the Bank of Japan to deal with any market turmoil, they said.
Major central banks are ready to use existing swap arrangements to supply emergency liquidity to address any shortage of dollar funding in the event of a Brexit vote.
Global markets are nervously watching the outcome of the referendum that is still too close to call, with investors and policymakers warning that a vote to leave the EU could unleash turmoil in financial markets.
Japanese policymakers are worried a Brexit vote would boost demand for the safe-haven yen and trigger an unwelcome yen rise that hurts exports.
The G7 nations have issued joint statements on an ad-hoc basis in the past to calm markets, such as when the Greek debt crisis intensified in 2012.