HARTFORD, Conn. — It’s now up to the Connecticut Senate, with its 18-18 partisan divide, to decide whether to approve a state employee labor concessions package that a handful of key conservative Democrats continue to review.

Senators are scheduled to vote Monday on the deal reached between Democratic Gov. Dannel P. Malloy and state employee union leaders. It comes a week after the House of Representatives, where Democrats hold a seven-vote majority, approved the agreement 78 to 72.

While the agreement is projected to cover $1.5 billion of the estimated $5 billion deficit in the new two-year state budget, which has yet to be finalized, there is disagreement about whether it saves enough and unnecessarily ties the hands of future legislators. House and Senate Republicans have argued that their budget proposals would provide even more long-term labor savings, while Democrats contend some of the GOP’s ideas would be illegal and privy to court challenges.

“What I’d like them to do is vote no on the union deal,” said Senate Republican Leader Len Fasano. He also said that “certain moderate Democrats” are “getting a lot of pressure” to vote in favor of the labor concession agreement and additional bargaining unit contracts. Democrats can ultimately approve the plan if all 18 of their senators vote yes and Democratic Lt. Gov. Nancy Wyman casts the deciding vote to break a likely tie.

“They should be left alone to decide, not politically but economically, whether or not this is a good deal or a bad deal for the state,” Fasano said of the Democrats.

On Thursday, Democratic Attorney General George Jepsen released a formal opinion requested by Democratic legislators that warned of substantial legal risks in attempting to change existing labor contracts by legislation. But it also noted how courts have some leeway in cases where the state is facing a severe “impairment,” such as a fiscal crisis.

Both Democrats and Republicans claimed the opinion supported their respective positions.

“The Attorney General’s opinion clearly highlights the constitutional dangers in the proposals put forth by the Senate and House Republicans. To represent the Republican plans as anything other than an extremely risky proposition is disingenuous,” said Senate President Martin Looney, a Democrat who accused the GOP of having an “anti-worker ideology.”

House Minority Leader Themis Klarides, a Republican, argued that nothing in Jepsen’s opinion undercuts the Republican budget proposals because the GOP hasn’t “proposed undoing any existing state contracts, but only want to make legal, statutory changes.” She argues the agreement with the State Employee Bargaining Agent Coalition, which negotiates health and pension benefits for most unionized state employees, will “put future Connecticut residents at peril” by essentially protecting those benefits until 2027 and including a four-year no-layoff provision.

Connecticut has been without a new two-year budget since the fiscal year began on July 1. Malloy, who proposed his own two-year state budget, has reluctantly been using his limited executive and spending powers to run state government. That has led to cuts in state funding to nonprofit social service agencies and the curtailment of local services provided by municipalities, who are uncertain about how much state aid they can receive.

A recent survey of city and town leaders, conducted by the Connecticut Conference of Municipalities, found 29 out of 61 communities surveyed have imposed some type of spending freeze during the current quarter of the fiscal year, such as holding off from spending money on police cars, public works equipment, new hiring and road work.