With Congress and the White House still struggling to agree on a response to the latest mass school shooting, U.S. Sen. Edward Markey on Monday presented a new proposal that would offer states incentives to adopt laws modeled off those in Massachusetts, where police have the power to approve or revoke gun licenses.

"The involvement of police chiefs in the licensing process is key. We can't overstate that enough," Markey said at a press conference at Boston Police headquarters in Roxbury.

Markey said his bill -- the Making America Safe and Secure Act -- would authorize the Department of Justice to hand out $20 million in grants each year for the next five years to states that adopt and maintain laws modeled on those in Massachusetts.

The senator said the focus would be on promoting laws that give law enforcement in other states the authority to deny, suspend or revoke a gun license, similar to what Massachusetts adopted as part of a 2014 gun law reform spearheaded by House Speaker Robert DeLeo.

"It is in part due to these laws that we have the lowest gun death rate of all 50 states," Markey said.

The senator was joined by Boston Mayor Marty Walsh, Sheriffs Steven Tompkins and Peter Koutoujian, Boston Police Commissioner Bill Evans, Stop Handgun Violence co-founder John Rosenthal and multiple local police chiefs.

"How many more mass shootings in schools do we need to have to move this needle forward?" Walsh asked at the news conference.

Toughening gun laws in other states, law enforcement officials said, is critical to safety in Massachusetts where over 60 percent of the guns used to commit crimes here come from other states.

Opponents of Massachusetts laws say they can trample Second Amendment rights, and that it would be better to spend the money on improving mental health care.

With reporting by State House News Service and WBUR's Anthony Brooks