NEW YORK (AP) — A new $12 million television ad campaign from Mayors Against Illegal Guns will push senators in key states to back gun control efforts, including comprehensive background checks.

New York City Mayor Michael Bloomberg announced the ad buy Saturday — just days after Senate Democrats touted stronger background checks while acknowledging insufficient support to restore a ban on assault-style weapons to federal gun control legislation.

"These ads bring the voices of Americans — who overwhelmingly support comprehensive and enforceable background checks — into the discussion to move senators to immediately take action to prevent gun violence," Bloomberg said in a statement issued by the group he co-founded in 2006.

The two ads posted on the group's website, called "Responsible" and "Family," show a gun owner holding a rifle while sitting on the back of a pickup truck.

In one ad, the man says he'll defend the Second Amendment but adds "with rights come responsibilities." The ad then urges viewers to tell Congress to support background checks.

In the other ad, the man, a hunter, says "background checks have nothing to do with taking guns away from anyone." The man then says closing loopholes will stop criminals and the mentally ill from obtaining weapons.

The Senate is scheduled to debate federal gun control legislation next month. On March 28, the group plans for more than 100 events nationwide in support of passing gun control legislation that includes background checks.

Mayors Against Illegal Guns and other gun-control advocates frequently cite a mid-1990s study that suggests about 40 percent of U.S. gun transfers were conducted by private sellers not subject to federal background checks. Based on 2011 FBI data, the group estimates 6.6 million firearms transfers are made without a background check for the receiver.

A spokesman for Bloomberg could not immediately say if the $12 million was coming from Bloomberg or the mayor's political action committee, Independence USA. The New York Times, which first reported the ad campaign Saturday night, said Bloomberg was bankrolling the ad buy.

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A spokesman for the National Rifle Association blasted Bloomberg and the new ads, saying NRA members and supporters would be calling senators directly and urging them to vote against proposed gun control legislation.

"What Michael Bloomberg is trying to do is ... intimidate senators into not listening to constituents and instead pledge their allegiance to him and his money," said spokesman Andrew Arulanandam.

Bloomberg has long supported efforts to curb gun violence, including sending New York City undercover investigators into other states to conduct straw purchases from dealers. Last month, Bloomberg's PAC poured more than $2 million into ads supporting Illinois state Rep. Robin Kelly, who won a special primary and ran partly on a platform of supporting tougher gun restrictions.

The new ads will air in 13 states the group believes are divided on gun control: Arkansas, Arizona, Georgia, Indiana, Iowa, Louisiana, Maine, New Hampshire, Nevada, North Carolina, North Dakota, Ohio and Pennsylvania.