ALBANY – New York State is poised to enact some of the nation’s strictest gun-control laws, with new prohibitions against sales of assault weapons, reduction in size of ammunition magazines, longer prison sentences for crimes committed with guns, and mandatory background checks for certain sales of firearms between private parties.

[Updates: The Assembly has started debating the bill.

Read the full text of the Assembly bill.]

The package of gun bills, pushed in the wake of the Dec. 14 mass shooting in which a gunman took 26 lives at a Connecticut elementary school and the Christmas Eve killing of two firefighters in the Rochester suburb of Webster, was being negotiated into the night Monday on the first day of the 2013 legislative session.

The State Senate passed the bill late Monday by a vote of 43-18; the Assembly is scheduled to take up the bill at 10 a.m. today.

Measures in the bill include reducing the size of ammunition magazines from the current 10 bullets to seven and expanding Kendra’s Law, the statute requiring mental health treatment in memory of a Fredonia woman who was pushed to her death in 1999 in front of a New York City subway train by someone with a long history of mental illness.

Lawmakers said the new provision will double the mandatory treatment period to up to a year and require mental health professionals to report to county mental health agencies about those patients they believe could be a danger to others. Counties will then pass that information on to the state Division of Criminal Justice Services, which can determine whether that person has a registered weapon and, if so, could confiscate any guns the person might own.

The looming deal also defines assault weapons as those with any single characteristic – such as a pistol grip or a telescoping stock or flash suppressor; current state law says assault weapons must meet two of those characteristics. The plan will grandfather in those gun owners who legally obtained assault weapons either before the 1994 ban was put in place or who bought them through what lawmakers described as loopholes being closed in the new deal. But such owners will not be able to transfer the weapons to other people in New York and will have to register the weapons with the state.

The deal includes closing a loophole in state law that has permitted assault weapons manufactured before 1994 to be sold.

“We’re not looking to demonize gun owners,” Gov. Andrew M. Cuomo said Monday night of the gun-control legislation he sent to lawmakers. He called on the Legislature to act quickly, in part, he said, because he is worried that there will be a run on assault weapons and large-capacity magazines in advance of passage.

The bill’s major provisions will take effect as soon as lawmakers pass it and Cuomo signs it.

“Time is of the essence,” Cuomo said, adding, “Enough people have lost their lives. Let’s act.”

Sens. Timothy M. Kennedy, D-Buffalo, and Mark J. Grisanti, R-Buffalo, voted to approve the New York Secure Ammunition and Firearms Enforcement Act of 2013.

Voting against were Republicans Patrick M. Gallivan, of Elma; Michael H. Ranzenhofer, of Amherst; George D. Maziarz, of Newfane; and Catherine M. Young, of Olean.

“I remain very concerned about the intrusion on individual rights, the rights of law-abiding citizens,” Gallivan said Monday night. “We now have more infringements on their rights when they haven’t done anything wrong.

“The intrusion on Second Amendment rights dealing with magazines and further restricting the type of weapon a law-abiding citizen can carry, there is not data to support that will make the streets safer.”

Under the bill, which the Assembly is expected to pass, there also will be new standardized handgun registration procedures put in place. District attorneys have been pushing for periodic gun reregistration laws; gun buyers in most areas of the state only have to register a gun when purchasing. The deal calls for gun owners to “recertify” with the state police every five years that the original information on their gun license is still valid.

Assembly Speaker Sheldon Silver, D-Manhattan, said the only major sticking point left in the negotiations was how to finance a provision that will permit schools to add extra security staff.

Senate Republicans met for nearly four hours behind closed doors, with members expressing concerns that the measure too broadly defines what the state will consider an assault rifle. Some senators, especially upstate Republicans in more conservative-leaning districts whose phones were ringing off the hook the last several days, were seeking to break the bill into pieces so they could vote yes on parts they support – such as expanded penalties for crimes committed with illegal guns – and oppose gun restrictions they say would violate Second Amendment ownership rights.

Cuomo said he will provide a message of necessity, a legal step that would allow the Legislature to quickly approve a bill instead of delaying for a three-day waiting period to permit advocates and opponents time to read and weigh in on any deal.

The governor, who has his eyes on a possible White House run in 2016, has been desperately trying to have New York be the first in the nation to push through stricter gun laws in the wake of the Connecticut tragedy.

The daylong, closed-door talks here came as Vice President Biden gave President Obama a list of proposals, including assault weapon bans and restricting large-capacity magazines, for the White House to try to get Congress to pass.

Gun rights groups condemned the nearing agreement. “It won’t do a damn thing to cut down on gun violence,” said Harold W. “Budd” Schroeder, head of the Erie County-based Shooters Committee on Political Education, a statewide gun owners advocacy group. He said that there was already talk about possible legal challenges to the gun restrictions and wondered aloud if the state was going to arrest people who do not turn in their high-capacity magazines or don’t reregister their guns.

The deal calls for a database of gun registrations now maintained by counties to be handled by the state police. The names of gun owners would not be subject to the state’s Freedom of Information Law, according to a copy of the agreement shown to The Buffalo News. Owners of guns now considered assault weapons would have a year to register their weapons with the state police; failure to do so could lead to a Class A misdemeanor and confiscation of the weapon.

While the size of ammunition magazines sold in New York would be reduced from 10 to seven bullets, owners who now have the larger-capacity magazines can keep them; but the deal would ban them from placing more than seven rounds in each.The Cuomo bill includes the “Webster provision,” which calls for life in prison without parole for people who kill first responders such as the two firefighters. It requires a buyer of a gun in a private sale to get a background check done by a gun store and requires stores to alert law enforcement when certain large purchases of ammunition are made. The legislation also increases penalties for gun possession on school grounds.

Gallivan said he has received at least 500 phone calls and emails from people opposing further gun restrictions. “It’s not just from people on the far right. One was a homeowner who doesn’t fish or hunt but said, ‘Enough of an intrusion on our rights,’ ” said Gallivan.

Ranzenhofer said he was concerned that the effort was moving too quickly. He said his office was being flooded with opposition calls and emails. He said the package fails to address a number of issues, such as efforts to better deal with school bullying.

“If I had assurances that this bill was going to change behavior and make communities safer,” he said, “I’d be a lot more comfortable. I don’t have that comfort.”