President Obama on Tuesday said the “biggest frustration” of his presidency is the country's unwillingness to enact gun control laws.

He cited Australian gun control efforts, which included the compulsory buyback of semi-automatic rifles, as a successful model for reducing mass killings, stating that the U.S. doesn't “have enough tools right now to make as big a dent as we need to.”

President Obama made his comments during a special question-and-answer session with Tumblr creator David Karp. While the session was supposed to promote the White House's legislative push on student loan debt, Obama responded to questions on a number of topics.

He gave his candid answer about gun control in response to a question from a student at the University of California-Santa Barbara, which is near Isla Vista, Calif., the site of a May killing spree that cost seven lives, including the assailant’s. The student asked what Obama would do to prevent more mass shootings on college campuses.

Obama responded that his “biggest frustration so far is that this society has not been willing to take some basic steps to keep guns away from people who can do unbelievable damage.”

He then cited Australia, which went well beyond basic steps following a 1996 mass shooting that left 35 dead. In the shooting spree's wake, requirements for licensing, registering and storing firearms were tightened.

Australia also instituted a national gun buyback that was compulsory for all semi-automatic rifles. The program collected 650,000 guns at a cost of $230 million, reducing the number of guns in private hands by 20 percent.

“Australia just said ‘Well that’s it, we’re not seeing that again,’ and basically imposed severe, tough guns laws,” Obama explained. “They haven’t had a mass shooting since.”

Obama went on to concede that the United States, unlike Australia, has a “different tradition” that “historically respect[s] gun rights.” Still, he said “it makes no sense” that the U.S. does not have in place “a fairly rigorous process so that you can’t just walk up to a store and buy a semi-automatic weapon.”

He did not go into detail about what such a process would look like, though he did list federal background checks as an example of commonsense policy he supports.

Recent gun control efforts, including a 2013 push for background checks, have stalled in Congress, but Obama has presided over some change in gun rules. Almost all of the change has been made without congressional approval.

The rigorous gun control process Obama says he wants cannot be implemented by executive action, so he called on his audience to demand change from legislators he says are “terrified” into inaction by the National Rifle Association and gun manufacturers.