Mayor Bloomberg is planning to spend $12 million for an ad campaign meant to pressure senators on gun control, administration sources said.

The national campaign kicks off tomorrow and targets states whose senators are on the fence, the sources said.

The TV ads will be aired in 13 states and push for universal background checks for gun buyers.

“These next two weeks during the congressional recess are critical,” said Deputy Mayor Howard Wolfson. “It’s important for senators to hear from their constituents before they vote.”

The ads, which will be put out through Bloomberg’s Mayors Against Illegal Guns coalition, feature a flannel-clad man sitting on the back of a pickup truck, cradling a shotgun while children play in the background.

“I believe in the Second Amendment, and I’ll fight to protect it. But with rights come responsibilities,” he says. “That’s why I support comprehensive background checks.”

The mayor has increasingly attacked the National Rifle Association and pushed for more stringent gun-control laws.

One of Bloomberg’s political action committees also helped end the campaign of an Illinois state senator after it released a string of attack ads over her past stance on gun control.

Meanwhile, last night the Mayor took a shot at Broadway at the annual Inner Circle show, where he donned a “Phantom of the Opera” costume over a Mark Zuckerberg hoodie in a skit that spoofed New Yorkers’ obsession with technology.

In the scene, Bloomberg whipped out an iPad and pokes fun at New York media while touting an app that could do his job for him.

Bloomberg took the stage at New York Hilton’s Grand Ballroom during the event, in which the mayor teams up with Broadway actors to to satirize current events and city policy.