A critical bill necessary to legalize casino gambling in Japan failed to get on parliament's agenda this week, jeopardizing a long-running effort to launch a potential $40 billion industry.

As a result, lobbyists and lawmakers said they believe it will be nearly impossible for the bill to get passed during the current parliament session, which ends June 22.

A committee on Japan's lower house won't have time to address the casino bill in its next session on Friday because it has to handle another item regarding the country's Atomic Energy Commission, a representative from the cabinet committee in charge of bill discussion told The Wall Street Journal Wednesday.

Friday was the only realistic date to discuss the casino bill to get it passed during the current parliament session, said Sakihito Ozawa, a senior official in the bipartisan group pushing the legislation, during a May 15 interview at his office. Bills traditionally need to be sent to the upper house at least 20 days before the session ends to enable passage, he said then.

Toru Mihara, an adviser to the 200-member bipartisan group pushing the bill, said Wednesday that he remained optimistic the bill would still be passed, just "not in the near future."

Some casino advocates such as Mike Tanji, executive adviser at Gaming Capital Management Inc., said they are now setting their sights on the next parliament session this fall.

But others are bracing for an even longer wait. "Since the coming fall session is short, it's unlikely we can pass the bill there. That means we will likely have to wait until next year's spring session," said Mito Kakizawa, a member of the bipartisan lawmaker group pushing the casino bill, in a recent interview.

In order for casinos to become legal in Japan, two bills need to be passed—the current bill, which asks the government to create a legal framework for casinos within one year, and a second bill detailing that framework. If the current bill were to go to a vote, it would likely pass easily due to support from the ruling Liberal Democratic Party and several others, proponents have said. But politicians have been reticent to use political capital on the sensitive matter, especially when other bills regarding issues like defense have become a government priority, they said.

Optimism had bubbled over in recent months that Japan could finally legalize casinos after more than a decade of lobbying, positioning the country to become the world's second-biggest gambling market after Macau. Casino-resorts have been sold as a way to bolster Japan's sluggish tourism industry as they have in Singapore, where visitor arrivals have risen some 60% since its two resorts opened in 2010.

Brokerage CLSA has pegged Japan's potential gambling revenue haul at $40 billion, more than six times the Las Vegas Strip's $6.5 billion total last year.

But in recent weeks, many proponents went from expressing near certainty the current bill would pass imminently to confidence they will instead be in for a longer battle.

Write to Takashi Mochizuki at This e-mail address is being protected from spambots. You need JavaScript enabled to view it