In a conference call Wednesday with mayors and other supporters of gun control, Vice President Joe Biden said the White House will continue to fight for together gun control measures beyond the Senate votes.
"That doesn't mean this is the end of the process," Biden said. "This is the beginning of the process."
A coalition of mayors also released its first television ad, featuring family members of those killed in the Connecticut school shootings calling on lawmakers to support "comprehensive and enforceable background checks."
"We cannot afford to wait for another tragedy. It's long past time for elected officials to listen to their constituents and pass reforms," said Michael R. Bloomberg, mayor of New York and co-chairman of Mayors Against Illegal Guns.
Bloomberg announced March 25 a $12 million television ad campaign running in 13 states that urges senators to support legislation expanding background checks for gun purchases. The mayor is founder and majority owner of Bloomberg LP, the parent company of Bloomberg News.
Wayne LaPierre, chief executive officer of the National Rifle Association, said Bloomberg's ad campaign will fail to persuade the public to support gun restrictions.
"They sure don't want him telling what self-defense firearms to own," LaPierre said on the same NBC program. "And he can't buy America."
LaPierre called universal checks "a dishonest premise. Criminals aren't going to be checked. They're not going to do this."
Josh Earnest, a White House spokesman, said Wednesday that a Senate vote on whether to ban military-style assault weapons represents progress, given how hard the president has pushed for tougher restrictions.
"I can't stand here and guarantee that it's going to pass, but it is a question that 100 senators are going to ask themselves when they wake up in the morning and look themselves in the mirror about whether or not they are going to — about which side they're going to be on when it comes to voting on a ban on military-style assault weapons," he said.