Obama joined military leaders and an estimated on-site audience of 4,000 at a memorial service on Sunday evening for the 12 victims who were killed at the Washington Navy Yard on September 16.
Speaking at Marine Barracks in Washington, Obama said he had witnessed five violent mass shootings during his time in office, and was worried that there has been a "creeping resignation" among the public that nothing can be done against "an epidemic of gun violence."
He noted that unlike countries such as Britain and Australia which acted after mass shootings, the US has not done enough to stop gun violence.
"And yet here in the United States after the round-the-clock coverage on cable news, after the heartbreaking interviews with families, after all of the speeches and all of the punditry and all of the commentary, nothing happens," said Obama.
"What's different in America is that it is easy to get your hands on a gun," said the president, acknowledging that "the politics are difficult".
"And that's sometimes where the resignation comes from, the sense that our politics are frozen and that nothing will change," said Obama. "Well, I cannot accept that."
Obama stressed that reducing gun violence is clearly "the change that we need" and overwhelmingly supported by the majority of Americans.
The shooting incident occurred on September 16 morning inside a building at the Washington Navy Yard that serves as the headquarters of the Naval Sea System Command. A total of 12 people were killed in the incident, excluding a suspect killed in the engagement with police and later identified as a 34-year-old navy contractor employee.
Obama: We need to end the epidemic of gun violence
Gun control is one of Obama's second-term legislative priorities. The Obama administration have tried for months earlier this year to build momentum for gun control reform at the national level, including inviting parents of the victims in last year's Sandy Hook Elementary School mass shooting to lobby for the measures.
However, key measures of the comprehensive gun control package, including banning assault weapons and expanding background checks for gun purchasers were defeated in Senate, dealing a major blow to gun control efforts led by the president.