The dollar rose past 85.00 yen in early Asian trade on Wednesday on expectations that the Bank of Japan would take more monetary easing steps under political pressure from the incoming government.
The dollar was at 85.10 yen shortly after 0000 GMT, the first time above 85.00 yen since April 2011 and up from 84.78 yen in Tokyo afternoon trade on Tuesday.
The Japanese currency has been declining as incoming prime minister Shinzo Abe, whose Liberal Democratic Party won a landslide national election last week, steps up pressure on the central bank to take bold easing steps.
Abe is to be named prime minister later Wednesday, after he swept to power on a hawkish platform of getting tough on diplomacy while fixing the economy with active fiscal spending and monetary easing.
On Sunday he threatened to change a law guaranteeing the central bank's independence if it did not agree to set a two-percent inflation target, in a bid to drag the country out of the deflation that has haunted its economy for years.
Abe, who previously served as prime minister from 2006 to 2007, is expected to name Taro Aso, another former prime minister in Japan's revolving-door political system, as finance minister and his own deputy, reports said.
As prime minister in 2008-2009, Aso launched a series of economic stimulus packages worth hundreds of billions of dollars to prop up Japan's long-struggling economy.