Senate support for extenders lacking

Reid will allow amendments to the bill later Thursday to shore up support for the legislation. 

"There's at least three I know that Republicans want to offer," the majority leader said on the floor. "There's a number on our side. But we will try to get that done as quickly as possible." 

Reid hopes to complete work on the bill before the weekend to ensure that a 21 percent cut in Medicare payments to doctors does not take effect. 

Assuming the bill passes the Senate, the House must approve changes made to it by the upper chamber before President Barack Obama can sign the package into law. 

House leaders have instructed members that they might be in session on Friday to vote on the Senate bill.