As the Group of Seven summit, Japan's biggest scheduled political event of the year, wrapped up on Sunday, Prime Minister Fumio Kishida was set to begin exploring the best timing for dissolving the House of Representatives for a snap election.

If Kishida is seen as having shown strong leadership at the gathering in his home constituency of Hiroshima, the approval ratings for his Cabinet may get another boost, triggering calls from ruling lawmakers for an early dissolution of the lower house.

Kishida might call a general election after his government in June unveils a policy package designed to combat Japan's rapidly declining birthrate, given that he has emphasized that focusing on child policies is the top priority of his Cabinet this year.

He is unlikely to wait much after that, to avoid seeing support for his administration dwindling in the wake of the start late in the year of full-fledged debate on possible tax hikes to fund the child-rearing programs, pundits said.

Group of Seven summit chair Japanese Prime Minister Fumio Kishida holds a press conference following the conclusion of the three-day event in Hiroshima, western Japan, on May 21, 2023. (Kyodo) ==Kyodo

In late April, his ruling Liberal Democratic Party won four out of five Diet seats up for grabs in by-elections.

Kishida's successful invitation of Ukrainian President Volodymyr Zelenskyy to the G-7 summit in the western Japanese city, devastated by a U.S. atomic bomb in 1945, is seen as a diplomatic achievement likely to bolster his support among voters.

Zelenskyy, who made his first trip to Japan since Russia invaded Ukraine in February 2022, participated in the summit in person, in a surprise move that prompted the G-7 leaders to unite further to support the Eastern European country.

Yukio Edano, former chief of the main opposition Constitutional Democratic Party of Japan, said Kishida could dissolve the lower house before late June.

Many lawmakers believe Kishida, who took office in October 2021, will seek a mandate before September 2024, when his stint as president of the LDP expires, adding if his party is victorious, he could be reelected party chief unopposed.

But while Kishida, who does not need to call an election until October 2025, will welcome any post-summit boost to his popularity, he is expected to be more focused on the public's responses to a pair of policies that could burden citizens with higher taxes -- budget increases for defense and support for families with children.

In December, the government decided to double its defense budget over a five-year period from fiscal 2023, aiming to bring annual spending to 2 percent of Japan's gross domestic product, on par with NATO members, amid the growingly severe security environment.

To cover the expanding budget, the Kishida administration plans to raise corporate, income and tobacco taxes, but has not elaborated on the timing of these steps, saying only that they will be implemented "at an appropriate time in fiscal 2024 or later."

Moreover, Kishida faces what he considers his most urgent challenge of tackling Japan's falling birthrate and shrinking population, eying steps certain to impose burden on taxpayers. He has pledged to take "unprecedented" measures to address the issue.

In late March, the government announced a draft policy package featuring the removal of income limits for child-rearing allowances and the introduction of enhanced benefits to cater to the specific needs of families with multiple children.

Kishida has expressed readiness to "double" the budget allocated for child support, but the exact amount and funding sources have not been clarified. His administration is scheduled to present a general framework on child-related policies in June.

Usually, discussions on a draft budget and a tax reform blueprint for the next fiscal year kick off after the summer within the government and the ruling camp. Depending on developments, speculation about large-scale tax hikes may mount later this year.

Tomoaki Iwai, a professor emeritus of political science at Nihon University, said that before calling a snap election, Kishida might also reshuffle his Cabinet, something previous prime ministers have often done in the past to freshen up the image of their governments.

Iwai added that Kishida is unlikely to be able to dissolve the lower house next year as he may be grilled over his controversial tax policies during the ordinary Diet session from January, leading to a decrease in support for his Cabinet.

Approval ratings for Kishida's Cabinet dropped to what is viewed as the "danger level" of 30 percent in late 2022, but have been recently recovering due in part to his diplomatic efforts, including a surprise visit to Ukraine on March 21.

Hiroshi Shiratori, a political science professor at Hosei University, said Kishida has become eager to dissolve the lower house at an early date as he appears to be worried about missing a favorable opportunity against a backdrop of unforeseen events.

For example, concerns about another financial crisis have been rising since the collapse of three major U.S. regional banks -- Silicon Valley Bank, Signature Bank and First Republic Bank -- earlier this year.

In 2008, then Prime Minister Taro Aso was forced to postpone dissolving the lower house in the aftermath of the financial crisis stemming from the bankruptcy of U.S. securities firm Lehman Brothers Holdings Inc.

Aso eventually called a snap election in August 2009, but the sluggish approval ratings for his Cabinet resulted in the ousting of the LDP from power for the first time in 15 years, with the then biggest opposition party scoring an overwhelming triumph.

Kishida may be afraid of the same fate repeating, Shiratori said, adding he would prefer to dissolve the lower house before debates on tax hikes attract the media spotlight.

(Tomoyuki Tachikawa in Hiroshima contributed to this story.)