The US Senate has rejected plans to tighten gun controls, including the restriction of weapons sales to people on terrorism watch lists.
Four proposals were brought before the Senate after 49 people died in an attack on a gay nightclub in Florida.
But Democratic and Republican senators voted along party lines, blocking each other's bills.
Senators strongly disagreed about how to prevent more attacks happening in future.
Republican Senator John Cornyn said: "Our colleagues want to make this about gun control when what we should be making this about is the fight to eliminate the Islamic extremism that is the root cause for what happened in Orlando.
"My colleagues in many ways want to treat the symptoms without fighting the disease."
For her part, Democratic Senator Barbara Mikulski said: "Why is it we would go through such incredible scrutiny to board an airplane to protect me against terrorist, and yet we have no scrutiny of the people on the terrorist watch list to be able to buy a gun?"
Eight days before the Senate's vote on Monday, Omar Mateen shot 49 people dead and injured many more in the worst mass shooting in recent US history.
Mateen was a US citizen who had been known to the FBI since 2013 but was not on a terrorism watch list.