Kentucky Sen. Rand Paul is on a mission to kill a proposal that would ban armor-piercing "green tip" bullets, the Daily Caller reported. The Republican, widely considered a presidential hopeful in the 2016 White House race, urged his backers to flood the Bureau of Alcohol, Tobacco, Firearms and Explosives with public comments to get the agency to back off the initiative.

In a letter posted to his political action committee's website, Paul attacks President Barack Obama for attempting to "cement his anti-gun agenda into law."

"I'm counting on your immediate action to help RANDPAC flood the agency with a message from America's pro-gun majority," the senator wrote. "Your grassroots muscle played a vital role in defeating President Obama's national gun registration scheme in 2013. And your support is needed again to defend our Second Amendment rights in 2015."

At the heart of the debate is a popular type of ammunition used for AR-15 semiautomatic rifles that until now has been exempted from the Bureau of Alcohol, Tobacco, Firearms and Explosives' 1986 restrictions on armor-piercing bullets, CBS News explained. Banning the 5.56-millimeter projectiles would help "protect the lives and safety of law enforcement officers from the threat posed by ammunition capable of penetrating a protective vest," the agency said.

White House press secretary Josh Earnest this week underlined the Obama administration's support for the bureau's effort, Reuters noted.

"This seems to be an area where everyone should agree that if there are armor-piercing bullets available that can fit into easily concealed weapons, that it puts our law enforcement at considerably more risk," the presidential spokesman argued.

But gun-rights supporters counter the administration's notion that the bullets are increasingly used in handguns and insist the "green tips" do not pose an increased risk for law-enforcement personnel.

Chris Cox, the executive director of the National Rifle Association, told Fox News earlier this week government statistics belie the proponents' arguments.

"The claim that this is done out of a concern for law-enforcement safety is a lie," Cox said. "The director of the Fraternal Order of Police has said this is not an issue of concern. And according to the FBI, not one single law enforcement officer has been killed with (this type of) ammunition fired from a handgun."