Two influential lawmakers have reached a deal on background checks for firearms, sources close to the negotiations told NBC News, a major breakthrough that sets the stage for a vote on new gun laws later this week. Pennsylvania Republican Sen. Pat Toomey and West Virginia Democratic Sen. Joe Manchin are set to announce their deal at an 11 a.m. press conference. Their compromise over President Barack Obama's call for universal background checks would exempt some transactions, such as those for gun sales between family members, according to NBC News. Both senators carry “A” ratings from the National Rifle Association and their support for expanding background checks beyond those for gun sales through licensed dealers could draw other Republican support. The development comes as up to 10 Republican senators indicated they would not support a filibuster led by colleagues Sens. Ted Cruz of Texas, Rand Paul of Kentucky and Mike Lee of Utah to prevent debate on gun legislation. The Senate could open debate on guns on Thursday.