"Our nation is on the cusp of whether it can maintain its societal functions," Kishida said in a policy speech at the opening of this year's parliamentary session, Reuters reported.
"It is now or never when it comes to policies regarding births and child-rearing - it is an issue that simply cannot wait any longer," he added.
Kishida said he would submit plans to double the budget on child-related policies by June, and that a new government agency to tackle the issue would be set up in April.
Japan saw a record low number of births in 2021, the latest data available, prompting the biggest-ever natural decline in the population.