One of the senators behind stricter background checks for gun sales struggled to hold back his tears when he met families who lost someone to the Sandy Hook massacre.
Senator Joe Manchin spoke to those who lost loved ones when crazed gunman Adam Lanza opened fire at the school in Newtown, Connecticut.
Manchin a Democrat, and Republican Patrick Toomey reached a bipartisan agreement on background checks, improving prospects for gun control legislation that Obama has been pushing for.
Scroll down for video
Grief: Senator Joe Manchin (left) becomes emotional as he meets with families of victims of the Sandy Hook Elementary School shooting in Newtown
Senator Manchin (seated on his own, right) hosted Newtown families in his Washington office on the day he announced that he had reached a bipartisan deal on expanding background checks on gun buyers
Senators reach deal over gun background checks
Obama said while it's not his bill and he wishes parts of it were stronger, the deal represents significant progress and if enacted would make it harder for dangerous people to obtain guns.
Senators plan to hold an initial vote Thursday to begin debating gun legislation. Obama says there is a lot of work remaining to enact gun control measures, including getting them through the Republican-controlled House.
More...
Six-year-old boy dies after neighbour, four, shoots him in the head with .22-calibre rifle as they played outside their homes
Tennessee boy, 4, accidentally kills wife of sheriff's deputy as he shows off his gun to a relative
Gabby Giffords still loves guns and her husband takes target practice with the same weapon that nearly killed his wife
He's calling on senators not to block consideration of the bill and for Americans to stay engaged.
Senators Manchin and Toomey said their accord would help keep firearms from criminals and the mentally ill.
Subjecting more firearms purchases to federal background checks has been the chief goal of Obama and gun control supporters, who promote the system as a way to prevent criminals and other potentially dangerous people from getting the weapons.
United: Mark Barden and Jackie Barden, parents of slain Daniel Barden, hold hands while meeting with the senator
David and Francine Wheeler (left), who lost their six-year-old son Ben in the shooting. Mark Barden, father of slain Daniel Barden (right)
Deal: Senators Joe Manchin (left) and Pat Toomey (right) proposed the deal on background checks for firearm purchases
Even so, the ultimate fate of gun legislation remains unclear, clouded by opposition from the National Rifle Association (NRA) and many Republicans and moderate Democrats in the Democratic-led Senate and the Republican-run House.
The NRA said Wednesday the group is unequivocally opposed to the plan and threatened to punish lawmakers in its ratings system.
'Expanding background checks, at gun shows or elsewhere, will not reduce violent crime or keep our kids safe in their schools,' top NRA lobbyist Chris Cox wrote in a letter sent to senators Wednesday night.
'Given the importance of these issues, votes on all anti-gun amendments or proposals will be considered in NRA's future candidate evaluations.'
The agreement between two of the most conservative members of each party was expected to make it even likelier that the Senate's initial vote Thursday to begin debating gun legislation will succeed, despite an effort by conservatives to block consideration of the measure.
DETAILS OF THE GUN DEAL
The proposal by Sens. Joe Manchin and Patrick Toomey would expand background checks to cover all sales at gun shows and over the Internet.
Those background checks would have to be accompanied by records proving to law enforcement officials they took place.
It would also exempt gun sales and transfers between friends and acquaintances without the help of an online intermediary.
'Truly the events at Newtown changed us all,' said Manchin, referring to the Connecticut town where 20 first-graders and six educators were shot down in December, launching the country into renewed debate over gun violence. 'Americans on both sides of the debate can and must find common ground.'
'I don't consider criminal background checks to be gun control,' said Toomey. 'I think it's just common sense.'
The administration was continuing its effort to pressure Congress on gun control on Wednesday as first lady Michelle Obama planned to visit a high school in Chicago, the Obamas' hometown, where authorities say 29 current or former students have been shot in the past year.
Currently, the background check system covers sales only by licensed gun dealers. The compromise would apply the system to all commercial sales, such as transactions at gun shows and online. The sales would have to be channeled through licensed firearms dealers, who would have to keep records of the transactions.
Private transactions that are not for profit, such as those between relatives, would be exempt from background checks.
The Obama administration has continued its efforts to pressure Republicans in restricting firearms, with Biden and Attorney General Eric Holder speaking at the White House Tuesday joined by law enforcement officials
Sen. Chuck Schumer, D-N.Y., who led an earlier unsuccessful effort to strike a bipartisan background check deal, is backing the compromise after changes were made from an initial version of the deal between Manchin and Toomey, according to a Senate aide who spoke on condition of anonymity to describe details of the talks.
The changes included eliminating language that would have required states to recognize permits to carry concealed weapons issued by other states and eliminating language that would have limited background checks to sellers who sell at least five guns annually, said the aide.
Some Republicans might vote to begin debate on the legislation but eventually oppose the measure on final passage. Other parts of Obama's gun effort already seem likely to face defeat, including proposed bans on assault weapons and high-capacity ammunition magazines.
Subjecting more firearms purchases to federal background checks has been the chief goal of Obama and gun control supporters
The gun legislation Reid wants the Senate to debate would extend the background check requirement to nearly all gun sales. Reid would try to replace that language with the Manchin-Toomey compromise once debate begins, a move that would require a vote.
The overall gun bill also tightens federal laws against illegal gun sales and slightly increases federal aid for school safety.
Thirteen conservatives have signed a letter saying they will block consideration of the measure, and Senate Minority Leader Mitch McConnell, R-Ky., said he will back that move. That will force Democrats to round up 60 votes to overcome the conservatives.
At least eight Republicans have said they want to begin debate or have indicated a willingness to consider it, a number that would be expected to grow if the background check agreement proves successful.
Some moderate Democrats were remaining noncommittal and could oppose opening the gun debate. There are 53 Senate Democrats and two independents who lean Democratic.
Amid the maneuvering, relatives of some Newtown victims are lobbying to support gun curbs. And Obama has been calling senators from both parties to push for the gun bill.
'People should listen to what we have to say and move the debate forward,' said Mark Barden, who lost his 7-year-old son, Daniel. 'It's not just about our tragedy. Lots of kids are killed every day in this nation. We have to help lead the change.'