It's not all happiness for one mother expecting her second child -- she frets about finding daycare for the coming baby.

"I'm worried about whether I'll be able to find a slot by the time I return to work," the 34-year-old office worker said as she played with her 6-year-old son in a park in the southwestern Japanese city of Oita.

There were 350 children on the waiting list for daycare in Oita as of April 2016, the eighth largest number among all Japanese municipalities. The figure rose to 463 this spring.

Across Japan, the figure was 23,700 as of April.

Prime Minister Shinzo Abe had previously pledged to slash the number of children on daycare waiting lists to zero by the end of next March under his growth strategy to get more women into the workforce.

But in May he postponed the target date by three years to the end of March 2021, citing an increase in working mothers resulting in more demand for childcare.

Critics and some lawmakers, including from the ruling camp, are skeptical about the feasibility of attaining the goal even under the three-year extension.

In Oita, a city government official attributed the local daycare shortage to an influx of population.

"People are coming in from other municipalities in Oita Prefecture and the population has been concentrated in one area," the official said, citing blocks around JR Oita Station where many apartments are being built. "Demand for daycare is rising."

The problem of population concentration is shared by many other prefectural capitals in the country.

The Oita city government plans to add slots for 941 children this fiscal year, more than double the previous year.

"The state government has postponed the target (of reducing children on daycare waiting lists to zero) to the end of fiscal 2020 but our city aims to attain the target next April," Oita Mayor Kiichiro Sato said.

He said that Oita needs to enhance childcare services so as to maintain its population, even though doing so may involve a huge financial burden.

Government efforts to tackle the daycare shortage began in 2001 after then Prime Minister Junichiro Koizumi pledged during his inaugural policy address at parliament to address the issue.

"Raising the issue during his first parliamentary speech reflected Mr. Koizumi's political savvy," said Mariko Bando, chancellor of Showa Women's University.

Bando, who at that time was director of the Cabinet Office's Gender Equality Bureau, said that back then, many Japanese believed mothers should stay at home until their children turn 3.

"Daycare was thus considered a necessary evil," she said.

Several years after Koizumi raised the issue, Japan's daycare capacity increased by 25,000 to 30,000 annually. The number of children on the waiting list fell from 25,000 in fiscal 2002 to 18,000 in five years.

In fiscal 2007, however, the growth of capacity began to slow down and the waiting list got longer again.

Bando attributed the slowdown to conservative forces in the ruling Liberal Democratic Party who advocate women staying at home gaining strength again.

The trend was prominent after Abe replaced Koizumi in 2006 in his first term as prime minister, she said.

Abe quit in 2007. After he returned to power in 2012, he changed his stance and began to advocate adding more female workers to the labor force as a pillar of his growth strategy.

A major obstacle to increasing daycare capacity is a shortage of daycare workers.

"We have to know that it takes time to develop human resources," said Konan University professor Masako Maeda, who served as deputy mayor from 2003 to 2007 in Yokohama, Kanagawa Prefecture, a city known for its ambitious efforts to overhaul its childcare system.

Maeda said building daycare centers at a rapid pace has caused a vicious cycle. A lack of staff leads to workers working overtime, and quitting due to exhaustion, with the tough working conditions putting off potential new recruits.

"When we built the centers, we should have trained a sufficient number of workers too," Maeda said.

The slow improvement has generated frustration and outrage among working mothers.

In February 2016, an anonymous blog titled "I couldn't get daycare -- die Japan!" went viral.

It prompted a protest against the daycare shortage among working parents in front of the Diet building in Tokyo. The opposition camp also called for an improvement.

One LDP lawmaker who served in a ministerial post said, "It used to be only natural that a mother quits her job to deliver her baby, and would never get so furious about daycare."

Konan University's Maeda said, "Substantial amounts of tax money must be injected to raise the wages for daycare workers. Taxpayers should also be braced for a burden."