Mayor Bloomberg has a new weapon against the nation’s lax gun laws — a billboard truck.

Mayors Against Illegal Guns — a coalition of 550 mayors Bloomberg has spearheaded — is sending the truck on a two-month trip across at least 25 states.

The truck has a big sign that says: “34 Americans are murdered with guns every day.”

“We have some failings in this country in terms of keeping guns out of the hands of minors, out of the hands of criminals, out of the hands of people with mental problems,” Bloomberg said yesterday on “Good Morning America.”