* Abe may lose "super majority" but still form govt
* Korean tensions boost Abe's leadership credentials
* Ruling party says "no political vacuum" during campaign
* Abe to order 2 trln yen package for child care, education
* "Nasty surprises" can't be ruled out - analysts (Adds Jiji report Abe news conference set for 0900 GMT in second paragraph)
TOKYO, Sept 25 (Reuters) - Japanese Prime Minister Shinzo Abe is expected on Monday to announce a snap election for next month to take advantage of improved ratings and opposition disarray, despite criticism that he is creating a political vacuum amid worries over North Korea.
Abe will hold a news conference at 6 p.m. (0900 GMT), Jiji news agency reported, after meeting party executives and will likely put pledges to spend on education and child care, stay tough on North Korea and revise the constitution at the forefront of his campaign.
Abe, whose ratings have risen to around 50 percent from around 30 percent in July, is gambling that his ruling bloc can keep its lower house majority even if they lose the two-thirds "super majority" needed to achieve his long-held goal of revising the post-war pacifist constitution to clarify the military's role.
A weekend survey by the Nikkei business daily survey showed 44 percent of voters planned to vote for Abe's Liberal Democratic Party (LDP) versus 8 percent for the main opposition Democratic Party. That was higher than the 27.7 percent a Kyodo news agency survey showed voting for Abe's party, with 42.2 percent undecided.
Abe's image as a strong leader has bolstered his ratings amid rising tensions over North Korea's nuclear arms and missile programs and overshadowed opposition criticism of the premier for suspected cronyism scandals that had eroded his support.
Given recent cases abroad where elections have led to unexpected results, however, political analysts are not ruling out what one called a "nasty surprise" for the Japanese leader.
Ruling Liberal Democratic Party senior official Koichi Hagiuda on Sunday brushed off concerns about a political vacuum during the election campaign.
"Even if there is a contingency during the election, I am confident that we can respond properly," Hagiuda said on public broadcaster NHK.
Opposition party officials have said calling an election would be an attempt by Abe to dodge questioning over the cronyism scandals in a session of parliament set to begin on Thursday. Abe is expected to dissolve the chamber that same day.
Sources have said Abe's election platform will see him promise to go ahead with a planned rise in the national sales tax to 10 percent from 8 percent in 2019 but increase the proportion of revenue spent on child care and education, delaying a target of putting the budget in the black in the fiscal year ending March 2021.
Abe will also tell his cabinet to compile a 2 trillion yen ($17.80 billion) economic package by year-end, composed mostly of spending on child care and education, government sources said. The Yomiuri newspaper said the funding would cover the three years from April 2018 until sales tax revenue kicks in.
The main opposition Democratic Party is struggling with single-digit ratings and much depends on whether it can cooperate with liberal opposition groups, while a new conservative party expected to be launched this week by allies of popular Tokyo Governor Yuriko Koike is racing to get ready for the vote.
A junior cabinet minister from the LDP, Mineyuki Fukuda, said over the weekend he would leave the ruling party to stand in the election from Koike's new group.
An LDP internal survey showed seats held by the LDP and its coalition partner Komeito could fall to 280 from the 323 they now hold, the Nikkei reported on Saturday. Reforms enacted last year will cut the number of lower house seats to 465 from 475.
($1 = 112.3400 yen) (Additional reporting by Takashi Umekawa; Editing by Michael Perry & Simon Cameron-Moore)