Leaders of nine Japanese political parties are appealing to voters in a debate the day before campaigning starts for upper house elections on July 21.

Prime Minister Shinzo Abe's ruling Liberal Democratic Party and its junior partner, the New Komeito Party, are expected to gain a majority of the 242 seats in the less powerful upper house through the election.

That would give them control of both houses of parliament, making it easier to pass legislation after years of gridlock.

Abe's Cabinet has enjoyed relatively high public support ratings since taking office in December, thanks largely to his ambitious economic revival program, including monetary easing and public spending. It has boosted business confidence, weakened the yen and lifted stock prices.