Peter Applebome / New York Times News Service

HARTFORD, Conn. — More than three months after the massacre of 26 people at Sandy Hook Elementary School in Newtown, Conn., legislative leaders announced Monday that they had agreed on what they called the most far-reaching gun-legislation package in the country.

It would require new state-issued eligibility certificates for the purchase of any rifle, shotgun or ammunition; include what legislators call the nation’s first dangerous weapons offender registry; mandate that offenders convicted of more than 40 weapons offenses register with the state; instate universal background checks for the sale of all firearms; and substantially expand the state’s existing ban on assault weapons.

But it did not include everything that anti-gun forces had asked for. It includes a ban on the sale of high-capacity magazines with more than 10 bullets. But despite a dramatic plea Monday from relatives of 11 of the victims killed at Sandy Hook on Dec. 14, legislative leaders did not include a ban on the ownership of high-capacity magazines, although they agreed on new rules requiring their registration. The legislation in Connecticut, agreed to after several weeks of negotiations between Democratic and Republican leaders in the Democratic-controlled General Assembly, was hailed by gun-control proponents as a landmark package and an appropriate response to the tragedy at Sandy Hook.

The bill is expected to go to both houses of the General Assembly on Wednesday; passage seemed assured. Leaders of both parties said the bipartisan process, which was more protracted than originally expected, had been difficult but should be a model for other states and for Washington.

Lawrence Cafero, the Republican House minority leader, said the legislation was drafted with the intent of balancing the rights of hundreds of thousands of gun owners with the public safety needs of the state. Asked how much support it would have among Republicans, he said, “Substantial.” Asked if it would be a majority, he declined to answer.

But Robert Crook, a lobbyist for the Coalition of Connecticut Sportsmen, said, “Whatever gun legislation they pass is not going to have an impact on anything that happened at Sandy Hook. The problem there was the individual and the mother.”

He said he had not seen all the elements of the bill, but took issue with the provisions to add more than 100 new assault weapons to those banned by the state.