Japan and the other Group of Seven economic powers need to demonstrate unity because the global economy is expected to "slow down considerably" with the widening U.S. subprime loan mess, according to Eisuke Sakakibara, the former senior Finance Ministry official known as "Mr. Yen."

The G7 financial leaders "should analyze the current conditions, reach a common position and confirm that they are ready to take joint action when necessary" at their meeting next Saturday in Tokyo, Sakakibara said in a recent interview.

Sakakibara, now a professor at Waseda University in Tokyo, said the G7 members — Britain, Canada, France, Germany, Italy, Japan and the U.S. — have already implemented steps to ease the confusion in global financial markets, such as providing liquidity and cutting interest rates.