(CNN) -- Senate Majority Leader Harry Reid formally introduced a much-anticipated gun bill Thursday, his office announced. The Senate is expected to debate the legislation when the upper chamber returns from a two-week recess.
The bill, released just over three months after the elementary school massacre in Newtown, Connecticut, is made up of three measures. One measure expands the background check system, while the other two deal with school safety and gun trafficking.
"The bill I advance tonight will serve as the basis for opening debate," Reid, the Senate's leading Democrat, said in a statement.
Reacting to the news that the Senate will consider a universal background check bill, NRA spokesman Andrew Arulanandam told CNN they are "strongly opposed" to the legislation, which was initially pushed by Sen. Charles Schumer, D-New York.
"We have made our position clear, and we will do whatever we can to defeat it," Arulanandam said.
The NRA has been running print and television ads in recent weeks against the idea of expanding background checks, and the group is expected to unveil news ads in the coming weeks.
"All options are on the table," Arulanandam added.
Reid will allow votes on amendments related to an assault weapons ban, high-capacity magazines and mental health provisions.
While there are some fierce advocates for the assault weapons ban, including Sen. Dianne Feinstein of California, Reid said earlier this week that he didn't believe the measure would get enough support on the floor but promised he would allow a vote through an amendment.
"In his State of the Union address, President Obama called for all of these provisions to receive votes, and I will ensure that they do," he said.
Vice President Joe Biden, who's been a leading voice from the Obama administration on gun violence, commended Reid via Twitter.