WASHINGTON (AP) - A Senate aide and a lobbyist say a deal has been reached on expanding background checks to more gun purchases.

It was announced Tuesday that Sens. Joe Manchin (D-WV) and Pat Toomey (R-PA) are scheduled to hold a press conference at 11 a.m. today to announce the progress of their bipartisan talks.

Meanwhile, the Senate is ready for an opening vote on restricting guns as Majority Leader Harry Reid, D-Nev., set a roll call for Thursday on starting consideration of the firearms legislation. Odds are growing that Democrats will win enough Republican support to thwart an effort by conservatives and Senate Minority Leader Mitch McConnell, R-Ky., to block consideration from even starting.
"I hope Republicans will stop trying to shut down debate and start engaging in the tough issues we were sent to Washington to tackle," Reid said.
Together, the developments were a boost for gun control advocates battling for restrictions in the wake of December's shootings that killed 20 first-graders and six staffers at an elementary school in Newtown, Conn.
Even so, the ultimate fate of gun legislation remains unclear, clouded by opposition from many Republicans and moderate Democrats in the Democratic-led Senate and the Republican-run House. Many critics say the proposal would violate the Second Amendment right to bear arms and burden law-abiding gun owners.
"We should focus law enforcement resources on the bad guys," said Sen. Ted Cruz, R-Texas.
Sens. Joe Manchin, D-W.Va., and Patrick Toomey, R-Pa., were expected to announce a background check compromise on Wednesday. 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 risky people from getting the weapons.
After weeks of negotiations, Manchin and Sen. Chuck Schumer, D-N.Y., told reporters late Tuesday that a gun control agreement was close.
The emerging deal would expand required background checks for sales at gun shows and online but exempt transactions like face-to-face, noncommercial purchases, said Senate staffers and lobbyists, who spoke on condition of anonymity to discuss the private talks. Currently, the checks are required only for sales handled through licensed gun dealers.
Though many details of the emerging agreement were unclear, Manchin and Toomey are among their parties' most conservative members and a deal could make it easier for some hesitant senators to support the background check measure, at least for now.
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.
The gun legislation Reid wants the Senate to debate would extend the background check requirement to nearly all gun sales. Assuming the deal between Manchin and Toomey is completed, Reid would try to replace that language with their agreement 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 McConnell 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.