At a special legislative session set to begin next week, the Maryland General Assembly will consider adding to the ranks of the state’s casinos and allowing them to expand their offerings beyond slots to include the likes of blackjack, craps and roulette.

This week, rank-and-file lawmakers have been relegated to a game of another sort: waiting.

Gov. Martin O’Malley (D) announced the session July 27, but his office has yet to release the bill that will be considered when the session opens Thursday. While the broad strokes are known — authorization of a Prince George’s County casino and Las Vegas-style table games — many key details are not. That has not made vote-counting easy.

“It’s certainly hard to know what we’re talking about,” said Del. Tom Hucker (D-Montgomery), reflecting the frustrations of many lawmakers. “It’s all relatively abstract without a bill.”

Chief among the unknowns: how much tax relief and other concessions O’Malley will propose giving to existing casino owners to compensate them for additional competition from Prince George’s. It’s also unclear who would make those calls — the legislature or a gaming commission — and when they would be made.

If such concessions are considered too costly for the state, O’Malley could lose votes from lawmakers who want to maximize the state’s take. If the concessions are not generous enough, some lawmakers could balk at a bill deemed unfair to existing owners.

Another wrinkle has also emerged in recent days: the possibility of allowing Maryland casinos to offer gambling over the Internet.

That idea — backed by the owners of Maryland Live!, the state’s largest casino — was mentioned in a memo that House Speaker Michael E. Busch (D-Anne Arundel) sent to his members on Wednesday. But on Friday, Busch appeared less than enthusiastic about the prospect.

“We’ve had no detailed discussions of that,” Busch told reporters after emerging from a couple of hours of meetings with House leaders. “It would be unfair for me to discuss something I know very little about.”

For the past two weeks, O’Malley has advertised the upcoming release of a draft bill so that lawmakers can begin studying its provisions.

On Friday, spokeswoman Raquel Guillory said the legislation would likely be made available “early next week.”

“It’s still a work in progress,” she said, echoing previous statements. “It’s a complicated issue.”

Less publicly, O’Malley aides have attributed delays to a delicate dance going on with Busch, who has been cool to the idea of expanding gambling.

During this year’s regular legislative session, the Senate passed two expanded gambling bills, both of which would authorize a Prince George’s casino, subject to a public referendum in November. Both bills died in Busch’s chamber.

When talking to reporters Friday, Busch said he and other delegates discussing the bill “were making some headway.”

“We’re just working through issues with the governor, things the House would like to see in the bill,” Busch said.

Among the things Busch identified were “fair” tax rates for existing casinos that stand to lose business to a Prince George’s venue and protection of existing host counties, which get a share of casino’s gross revenues.

Busch provided no details, and neither did two delegates who emerged from meetings before him and spoke briefly to reporters.

“There’s no final bill yet, so there’s not much to talk about,” said Del. Eric G. Leudtke (D-Montgomery), who served on a gambling work group this spring.

“Check with the governor’s office, not us,” added Del. Sheila E. Hixson (D-Montgomery), chairwoman of the House Ways and Means Committee, which has jurisdiction over gambling legislation.

Few lawmakers seem to be relishing their return to Annapolis next week. Many have had to reschedule summer vacations or juggle plans to attend conferences.

Among those is Melony G. Griffith (D-Prince George’s), who chairs her county’s legislative delegation. She is among 17 legislators signed up to attend this year’s National Conference of State Legislatures conference in Chicago and would have to hurry back.

Members of the Prince George’s delegation, which remains divided about the prospect of hosting a casino, had tentatively planned to meet this weekend to review the details of the bill. Without a bill, that plan has been scrapped.

“It makes a complicated process even more complicated,” Griffith said.

“The time to deliberate and comb through the details of the bill just doesn’t exist before the session,” Griffith said. “There’s a question of how much opportunity we’ll have to shape the legislation.”

Senate Minority Leader E.J. Pipkin (R-Cecil) was a little more blunt in a press release he issued this week headlined: “Pipkin to O’Malley: Where’s the bill?”

“The special session starts in less than a week,” Pipkin wrote. “The governor has had all summer to craft the proposal. Where’s the bill?”