Republican presidential candidate Sen. Marco RubioMarco Antonio RubioOvernight Cybersecurity: Bipartisan bill aims to deter election interference | Russian hackers target Senate | House Intel panel subpoenas Bannon | DHS giving 'active defense' cyber tools to private sector Senators unveil bipartisan push to deter future election interference Puerto Rico's children need recovery funds MORE (Fla.) ripped President Obama's new gun control measures Tuesday, calling him "obsessed" with the issue.

"It undermines the Second Amendment, and it will do nothing to keep people safe," Rubio told Fox News's Bill Hemmer during an interview aired on "America's Newsroom."

"Barack ObamaBarack Hussein ObamaMcCarthy: ‘No deadline on DACA’ Democrats will need to explain if they shut government down over illegal immigration Trump’s first year in office was the year of the woman MORE is obsessed with undermining the Second Amendment — an important protection our Constitution recognizes and defends for us, and he's looking for any way possible to undermine it. He's been doing this forever," Rubio said. 

Republicans have panned Obama's move to expand background checks for people buying firearms online or at gun shows, and at least one lawmaker has floated withholding funding from the Department of Justice to stop him.

Obama's executive action comes just a week before his final State of the Union address. By tackling background checks head on, he is keeping the spotlight on the gun issue just weeks before the first ballots are cast in the presidential race to succeed him.

"This president is obsessed with undermining the Constitution in general, but the Second Amendment in particular. He is obsessed with undermining it, and it will do nothing," Rubio said Tuesday.