Japan's pro-casino lawmakers have agreed to consider setting limits on Japanese nationals' entry to casinos, bowing to pressure from opponents who threatened to block a legalization bill unless it addressed issues such as gambling addiction.

Japan's parliament is expected in the coming weeks to discuss legislation that would be an essential first step to unlock a gaming market some analysts say will be worth tens of billions of dollars a year.

The revision would boost chances that the bill will be passed this year as proponents hope, although it is not yet clear whether enough anti-casino lawmakers will be persuaded to provide the support it needs in both houses of parliament.

"The government, for the purpose of preventing the negative effects of casino facilities by non-foreign visitors, will take necessary measures regarding admittance and capacity...," said the amended section to the bill, a draft of which was shown to reporters on Thursday.

The revision would avoid banning Japanese entry outright and limiting casinos to foreign tourists, pro-casino lawmakers said. Some Japanese media reports said such a ban might be adopted to ensure passage of the bill.

Prime Minister Shinzo Abe has said casino resorts would help the economy by boosting tourism. But market researchers say Japan's 128 million people would likely account for a majority of casino revenues and casino operators have said foreigner-only resorts could struggle to make a profit.

"From our standpoint, I will say that we will not be interested in Japan or any other country on a foreigners-only basis. We can't do that. Our business model won't allow it," Sheldon Adelson, CEO of the world's largest casino operator Las Vegas Sands Corp, told analysts on a conference call on Wednesday.

Hiroyuki Hosoda, chairman of the pro-casino lawmakers' alliance, said the revision was in response to concerns over gambling addiction and money laundering. Such worries should not hold up the current bill, he said.

A second bill, set to be drafted next year if the current bill passes by year-end, would address specifics including possible entry fees or conditions for entry by locals, Hosoda said.

He told reporters the current priority was to set in motion the legalization process for a casino industry, stressing its importance to Japan's economy.

"With the manufacturing sector weakened, it's time for the Japanese to aim for economic growth through tourism," he said.

Abe has said he hopes casinos will be legalized in time for the 2020 Olympic Games. Analysts have said any delays in legislation will make that difficult.