New York City Mayor Michael Bloomberg has announced a massive new television advertising campaign that will push senators in key states to back gun control efforts.
The 12 million dollar (£8 million) Mayors Against Illegal Guns advertising blitz will press for comprehensive background checks.
Mr Bloomberg is one of the most prominent gun control proponents in the US, and the launch comes just days after Senate Democrats touted stronger background checks while acknowledging insufficient support to ban assault-style weapons.
He said: "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."
Mr Bloomberg co-founded Mayors Against Illegal Guns in 2006 and it now has more than 800 mayors from around the US
President Barack Obama vowed to push for tighter gun controls laws in the wake of the December massacre of 20 young children at a Connecticut elementary school, by a gunman using a military-style assault rifle. The Senate is scheduled to debate gun control legislation next month after returning from the Easter Recess.
Most congressional Republicans, some Democrats and a wealthy pro-gun lobby remain opposed stricter gun laws. Many Americans see gun ownership as a legitimate option for self-defence and a basic right enshrined in the US Constitution.
In two ads posted on website of Mayors Against Illegal Guns, a gun owner holds a rifle while sitting on the back of a pickup truck. The man says he will 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". He then says closing loopholes will stop criminals and the mentally ill from obtaining weapons.
A spokesman for the National Rifle Association, the country's most powerful pro-gun group, criticised Mr Bloomberg and the new ads. "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.