New York City Mayor Michael Bloomberg is backing a $12 million television ad campaign advocating universal background checks for gun purchases that will start airing in "key states" during the congressional recess.

The campaign -- aimed at influencing an upcoming Senate gun-control vote -- was announced Saturday by Bloomberg and the Mayors Against Illegal Guns organization, of which he is co-chairman.

Bloomberg's office did not immediately respond to questions about the source of the ad funding.

The ad campaign comes days after Senate Democratic leadership decided not to include an assault weapons ban in the legislation it plans to bring to the floor next month.

Two of the planned ads previewed Saturday online feature a man who is holding a gun.

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"For me, guns are for hunting and protecting my family," he says. "I believe in the Second Amendment . . . but with rights come responsibilities. That's why I support comprehensive background checks for criminals and the dangerously mentally ill."

Neither ad mentions assault weapons.

The spots will be aired in states represented by both parties, "where they can influence the upcoming Senate vote," according to a statement from the mayors group. Those states include Arizona, Indiana, Louisiana, Maine and Pennsylvania.

Congress is on recess until April 8.

"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 the statement.