The NRA wants Congress to fund more armed guards at schools, step up prosecutions of people who file false gun applications and increase the background check system's access to state records of people with serious mental illness and other problems.
Sen. Charles Grassley of Iowa, top Republican on the Senate Judiciary Committee, said of Reid's announcement, "I don't know how the leader expects members to vote on an ever-changing piece of legislation that has yet to gain bipartisan support."
If not included in the overall gun bill, an expansion of background checks could have been offered as an amendment. But that would have likely meant it would have needed support from 60 of the 100 senators to prevail — a difficult hurdle for Democrats.
Including expanded checks in the gun legislation signals either of two courses by Democrats: A feeling that they can win bipartisan support for the measure, or a willingness to essentially challenge Republicans to reject the entire gun-control package and face the political consequences in next year's elections.
It also pleases gun control backers who have said that in response to the Newtown killings, they expect Congress to do more than toughen gun trafficking penalties and boost school safety aid.
"Senator Reid's announcement is a tremendous step and we recognize there is still a tough road ahead," said Dan Gross, president of the Brady Campaign to Prevent Gun Violence, adding that his group would activate supporters to contact lawmakers.
"The majority leader's been a pretty steady guide throughout, and this a good example," said Mark Glaze, director of Mayors Against Illegal Guns, a group New York City Mayor Michael Bloomberg helps lead.
Reid said during next months' debate, he will allow votes on amendments including an assault weapons ban, curbs on high-capacity ammunition magazines and mental health. There is wide-ranging agreement that many states poorly report mental health records to the federal background check system.