One of the biggest issues facing gun control in New York is the vast supply of handguns, NYPD Commissioner Ray Kelly said Monday.

Speaking to Face the Nation, Kelly voiced support for an assault weapons ban but outlined that those weapons only account for two percent of those arrested for gun possession.

"The problem is the handgun. 60 percent of the murders in New York City are caused by handguns, and we simply have too many of them," the commissioner said, before citing last year's record low levels of murder in NYC.

“In our city, 90 percent of the guns we confiscate are coming from out of State.”

According to Kelly, a universal background check, one of the four measures President Obama asked Congress to pass earlier this month, would help towards cutting back on the illegal sale of guns.

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“I think over time a universal background check will have an impact.”

Kelly also spoke about new gun detector ‘terahertz’ technology that the department is developing with the Defense Department and the London Metropolitan Police.

“We have tested it, we just received the latest prototype and it’s very encouraging.”

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"It's still too big for deployment in a reasonable way. It's sort of like the cellphone was 20 years ago. We hope to be using it experimentally in the next 6 months."

Watch the ‘Face the Nation’ Interview below

New York City Police Commissioner Ray KellyMarc Asnin/Redux