UPDATED 7:58 a.m. Suspense is building in Hartford, where lawmakers are waiting to see if they will have to scramble to fill a $1.6 billion hole in the state budget.

With just one week left until the new fiscal year, the tentative agreement Gov. Dannel Malloy reached last month with state employee unions on cost-saving concessions now appears headed for collapse. While voting among the the 15 unions will not conclude until Friday and a majority of state employees have already approved the deal, the state’s largest union, heavy opposition within Council 4 of the American Federation of State, County and Municipal Employees (AFSCME) has sunk nearly all hopes that the deal can be salvaged.

Under the voting rules of the State Employees Bargaining Agent Coalition, which negotiated the agreement on behalf of all state unions, two conditions are necessary for ratification: approval by 14 of the 15 unions and approval by 80 percent of all union membership. Because of the size of AFSCME’s membership and the fact that another union has already voted against the agreement, both conditions look set to fail.

In anticipation of that outcome, Malloy called for a special session of the state legislature to plug the deficit that would result.

“I am loathe to make the decisions facing us at this juncture — including layoffs, programmatic and municipal aid cuts — but I am left with no choice,” he said in a press release.

In order to fill a $2 billion gap in the state budget for the next two years, Malloy asked the state’s 45,000 employees to accept changes to their health benefits, pensions and wages. On May 13, Malloy announced that he secured $1.6 billion of that gap in a tentative agreement with union leaders, the remaining $400 million coming from additional spending cuts and existing revenues.

But if, as now appears likely, that agreement is not ratified by the unions, Malloy will compensate for it with a “Plan B” budget, which includes thousands of layoffs, severe cuts to state services and a tightening of the flow of money from the state to municipalities.

The last consequence would have significant ripple effects for New Haven, which is the second-largest recipient of state aid.

Malloy administration officials said Wednesday that they would be open to a re-vote, the Mirror reported, but not to new terms.

Final results of the voting may not be available until Friday morning.