After lashing out at Pyongyang over its repeated provocations, Abe stated: "Elections that are the starting point of democracies should not be affected by any threats that may emerge from North Korea".
Japanese prime minister Shinzo Abe has called an election a year early, in a surprise move created to shore up his power.
The prime minister is scheduled to hold a press conference at 6 p.m., at which he is expected to formally announce the dissolution.
According to The Japan Times, opposition lawmakers have slammed Abe's plan as a violation of the constitution and accused the Prime Minister of dissolving the chamber in a bid to avoid being grilled over allegations of cronyism that are expected to take place on Thursday, the same day Abe plans to dissolve the chamber.
The main opposition Democratic Party, which held power between 2009 and 2012, drew only 8 percent support. Abe said that he will dissolve the lower house of Parliament and call elections in October.
Koike, who is a former member of Abe's Liberal Democratic Party, said that she would lead candidates across the nation.
That was higher than the 27.7% a Kyodo news agency survey showed voting for Abe's party, with 42.2% undecided. Nikkei Research Inc. surveyed 1,044 people aged 18 or older by phone.
A weekend survey showed that 44% of voters planned to vote for Abe's Liberal Democratic Party, against just 8% for the opposition Democratic Party.
Sixty-four percent said they don't support his drive for a fresh mandate, the report said, without giving details on the number of respondents or margin of error. While unemployment is less than 3 percent, the premier has said wage rises have fallen short of his expectations.
Other government sources have told Reuters Abe will pledge to use some of the revenue from a scheduled sales tax hike in 2019 to fund spending on education and child care.
Nevertheless, roughly a fifth of those canvassed by Nikkei answered that they had yet to make up their minds, meaning it was unclear whether Abe would be able to muster the two-thirds parliamentary majority he needed in order to pass a Constitutional reform.
But he was given a lower house seat in the southern Kanto bloc through proportional representation.