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WASHINGTON — President Donald Trump has directed his attorney general to propose regulations that would ban bump stocks and similar devices "that turn legal weapons into machine guns," the president announced Tuesday.

Trump, speaking at the start of a Medal of Valor ceremony at the White House, said he expected the "critical" new regulations to be finalized soon.

A Justice Department review of bump stock regulations started in December, Trump said, after America's deadliest mass shooting in Las Vegas left 58 people dead. The gunman in that incident used bump stocks that allowed him to engage his weapon's trigger faster, making it fire similar to the rate of an automatic weapon.

Regulations on bump stocks have garnered recent support from both sides of the gun control debate, but Trump's move goes further than the tepid support his administration had offered last year.

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After Trump's Tuesday announcement, president and CEO of the AR-15 Gun Owners of America, Chris Waltz, told NBC News that his group understands "why the president is taking these steps" and believes "that devices are designed to allow semi-automatic rifles to function like fully automatic rifles should be subject to additional regulations.”

The National Rifle Association, which has taken much of the heat in the gun control debate, was reserving judgment of the president's action until "an actual rule is published with specifics that we can review," NRA spokeswoman Jennifer Baker said in a statement.

"The NRA’s stance on this issue has not changed. Fully-automatic weapons have been heavily regulated since the 1930’s, but banning semi-automatic firearms and accessories has been shown time and again to not prevent criminal activity and simply punishes the law-abiding for the criminal acts of others," Baker said.

In the memo, Trump asked that the DOJ propose the rule "as expeditiously as possible," while also straying to call out the Obama administration for not taking action of their own.

"Although the Obama administration repeatedly concluded that particular bump stock type devices were lawful to purchase and possess," Trump's memo states, "I sought further clarification of the law restricting fully automatic machine guns."

President Barack Obama's administration repeatedly pressed for more gun control measures, especially in the wake of the tragic shooting at Sandy Hook Elementary School, although at that time, the Bureau of Alcohol, Tobacco, Firearms and Explosives did ultimately decide it could not legally regulate bump stocks. It is unclear how Trump's administration believes it will avoid similar legal quandaries as it presses forward on the issue.

The steps proposed by President Trump Tuesday would not have affected the attack at a high school in Parkland, Florida, less than a week ago that left 17 students and teachers dead.

The White House will hold listening sessions with parents, teachers, and students from Parkland, as well as others affected by school shootings in Newtown, Connecticut, and Columbine, Colorado, on Wednesday.

Just before the Trump's announcement, Press Secretary Sarah Huckabee Sanders also reiterated the president's openness to making the background check process "more efficient."

Though Trump will be listening at Wednesday's sessions, he hasn't signaled any openness to the introduction of new gun control measures — nor has he mentioned that possibility in his remarks on gun violence in the aftermath of Parkland.

On Tuesday, he again cited a need for officials to do more on "mental health" and bettering coordination efforts for "swift action" when there are known warning signs that may signal potential shooters.