Prime Minister Shinzo Abe's ruling bloc is headed for a big victory in this month's upper house election, media surveys show, a win that would end a parliamentary deadlock and set the stage for Japan's first stable government since 2006, according to Reuters.

The anticipated victory would give the Japanese leader a mandate for his "Abenomics" recipe that aims to end prolonged stagnation with a mix of hyper-easy monetary policy, fiscal spending and structural reforms including deregulation.

However, a big win could also be a mixed blessing if members of his Liberal Democratic Party (LDP), buoyed by victory and with no national election required until 2016, oppose painful reforms many say are needed to revive growth.

Newspaper surveys taken on July 4-5 and published on Saturday showed the LDP and its coalition partner, the New Komeito party, were on track to win more than 70 of the 121 seats up for grabs in the July 21 poll for the 242-seat chamber.

With the coalition's 59 uncontested seats, that would hand them a hefty majority and end a "twisted parliament" in which the opposition controls the upper house, hampering policy implementation.