HARTFORD, Conn. — Connecticut lawmakers narrowly approved a labor concessions agreement on Monday, hoping it will bring them closer to finalizing a new, two-year state budget.

The evenly split Senate voted 18-18 in favor of the agreement, which is projected to cover $1.5 billion of the state’s estimated $5 billion budget deficit over the next two years. Democratic Lt. Gov. Nancy Wyman then broke the tie by voting in favor of the agreement reached between her running mate, Gov. Dannel P. Malloy, and union leaders.

The House of Representatives approved the same deal last week, 78-72.

Democratic Senate President Martin Looney of New Haven said he hopes Monday’s approval will finally lead to a new, two-year budget. Connecticut has been without a plan in place since the fiscal year began July 1, requiring Malloy to run the state using his limited spending authority. That has led to cuts to social service agencies and the curtailment of local government services.

“At least today, we will have adopted a substantial pillar to get us toward that budget,” said Looney, noting how lawmakers now must figure out how to cover a two-year, $3.5 billion deficit. A typical annual budget is roughly $40 billion.

It’s questionable, however, whether any final state budget deal will be bipartisan.

Senate Republican Leader Len Fasano of North Haven said the “onus” is now on Democrats to produce a budget, noting they have dismissed GOP budget proposals. Both Senate and House Republicans contend their plans would create more long-term savings than Malloy’s concessions deal by imposing changes to state employee working conditions by state law, which Democrats argue would prompt legal challenges.

“I believe we’ve closed off an avenue that’s going to come back and bite many of us,” Fasano said of the labor deal vote. He said those who voted for the package “cannot cower when a budget comes forward” that now includes tax increases and cuts to social services and aid for cities and towns.

“Understand what you’re doing when you vote today. Understand the path that you’re going down,” Fasano warned his Democratic colleagues.

The ratified labor agreement includes four years of job security in return for concessions such as a three-year wage freeze, three furlough days, higher insurance premiums and insurance co-pays and a new hybrid pension-401(k)-style retirement plan for new state employees. It marks the third concessions package approved by rank-and-file state workers during the past decade, prompting union leaders to demand that state lawmakers now increase taxes on the wealthy and corporations to help cover the remainder of the budget deficit.

“In Connecticut, the very wealthy pay a lower percentage of their income in state and local taxes than working and middle-class families do. This is a level of (unfairness) and we hope the General Assembly passes a fair and moral budget for all Connecticut residents,” the State Employee Bargaining Agent Coalition said in a statement released after the vote.

It’s been unclear whether Democrats would have enough support to pass the labor-savings deal. In the days leading up to Monday’s vote, several conservative Democrats would not declare support for the package. To garner their votes, Looney promised to bring up some reforms the lawmakers requested during the budget negotiations, such as requiring a vote by the General Assembly on all union contracts.

One of those lawmakers, Sen. Gayle Slossberg, D-Milford, said she was “not so comfortable” with some parts of the deal, such as extending health and pension benefits until 2027. But she called it “a reasonable package” and “not a bunch of giveaways.”

“Without this agreement, we will have a $1.57 billion hole to address in our budget and we will lose the long-term health care savings and pension that have been negotiated,” Slossberg said. “And that’s a very big hole in a very big deficit.”