Japan's plan to open up to casino gambling has been delayed again, three people familiar with the process said, dealing a blow to one of Prime Minister Shinzo Abe's policy priorities and to hopes the first resort will open in time for the 2020 Tokyo Olympics.

Pro-casino lawmakers have given up debating a casino legalization bill this month and now aim to start discussions in November, two people directly involved in the process and one person briefed on the deliberations said on Wednesday.

Companies such as Las Vegas Sands Corp and Caesars Entertainment Corp are vying to win the first licenses to operate casinos in Japan, a market that brokerage CLSA estimates could generate annual revenue of $40 billion.

Authors of the casino bill previously planned to start discussions around this week and vote on the bill in November. The delay will make it harder to enact the law by the end of this session of parliament on Nov 30, the sources told Reuters.

Putting off passage until the next session, expected to start in early 2015, would in turn make it less likely a casino could open in time for the Olympics, as people following the process have said tough logistics make this target a close call.

"We are aiming for early November now," said one parliamentary source who was involved with drafting the bill, regarding the start of parliamentary debate. He declined to be named because plans were not yet official.

Even before the latest delay, Keiichi Ishii, policy chief of Komeito, the junior partner in Abe's coalition government, told Reuters on Monday: "The hurdle is quite high for both lower and upper houses to enact (the legislation) during the current session."

Debate on legalizing "integrated resorts" has been delayed by other legislation as well as opposition from lawmakers worried about gambling addiction and other issues.

Failing to pass the bill this year would mean pushing back the drafting of a crucial second bill on implementation, which is partly meant to address concerns from some Komeito members. Many say the second bill may prove even harder to pass as it covers more details such as regulations.

Abe has called casinos a pillar of his economic growth policy, but some Komeito members are opposed due to worries about gambling addiction.

The opposition Democratic Party is divided: some of its members helped author the bill, while others are demanding more thorough debate over the possible risks, such as addiction and crime, before voting on the bill.

The delays are sure to disappoint casino developers, but Caesars said it was not discouraged.

"Caesars is certainly still interested in pursuing an IR (integrated resort) license in Japan even if the resort could not open in time for the Olympics," Steven Tight, head of the company's international development division, told Reuters.

"But the sooner the IR Promotion Bill is passed, the sooner Japan can realize the many benefits generated by an integrated resort."

Sands declined to comment on the latest delay.