Tokyo - Japanese Prime Minister Shinzo Abe on Sunday vowed to impose "all possible pressure" on North Korea over its nuclear and missile programmes, promising to secure national security in a televised debate before a snap election.Official campaigning begins on Tuesday for the October 22 election in the world's third largest economy.Two missiles"Stepping up all possible pressure, we need to create a situation in which North Korea wants talks as it will change policy," Abe told the debate."We will protect our country under stable politics".Abe is seeking a new term as tensions with North Korea rise, with Pyongyang in recent months conducting what it described as a hydrogen bomb test and firing two missiles over Japan.His Liberal Democratic Party (LDP), which has ruled the country for most of the post-war era, is on course to secure a majority. But it is unclear whether it can again capture some two-thirds of the 465 seats in the powerful lower house, the margin necessary to approve changes to the pacifist constitution which Abe has been pushing.The Democratic Party (DP) - previously the main opposition party - imploded last week but Abe faces a new challenge from popular Tokyo governor Yuriko Koike.The pair clashed during the TV debate over economic and other policies.Huge government spendingFormer TV anchorwoman Koike has shaken up Japan's usually sleepy political scene by launching her "Party of Hope", vowing a break with the old school represented by Abe's LDP. "We offer an alternative to voters in order to correct the Abe-dominated politics," Koike told the live debate."Our big goal is to aim to take power," the media-savvy Koike said without elaborating.Abe defended his growth plan dubbed Abenomics - a mixture of aggressive monetary easing and huge government spending along with reforms to the economy intended to pull the country out of decades of deflation and downturn."If we had not carried out the monetary policy, the fiscal policy and the growth strategy, terrible things would have happened," he said.