Previously unknown outside of gun enthusiast circles, the device received attention after it was revealed that the Las Vegas shooter used them during the rampage that killed 58 people and injured over 700.
President Trump's Friday tweet also attempted to blame President Obama for having "legalized" bump stocks in the first place, a misleading reference to how the original ATF review of the devices happened during the Obama administration.
The announcement comes a day before large numbers of protesters are expected to descend on Washington, DC for "March for Our Lives", a rally organized to push for stricter gun laws in the wake of the school shooting in Parkland, Florida last month.
Attorney General Jeff Sessions said in a statement the ban "is a critical step in our effort to reduce the threat of gun violence that is in keeping with the Constitution and the laws passed by Congress".
He tweeted on Friday that "We will BAN all devices that turn legal weapons, into illegal machine guns".
Trump took on the bump-stock issue in the aftermath of last month's Florida shooting, as students, victims' families and gun-control advocates launch their push for a re-examination of current gun laws.
Jeff Sessions, the U.S. attorney general, has officially proposed a rule that would effectively ban bump stocks, devices that turn semi-automatic weapons into fully automatic weapons.
The regulation will go through a standard 90-day period for public comment, so it could see changes within that time or simply be put into effect as is.
In the proposed rule, the ATF says it has now concluded that the previous decision "does not reflect the best interpretation of the term "machine gun" under the law.
Fully automatic weapons have been banned in the USA since 1986, but bump stocks were described by the ATF in 2010 as "a firearm part and is not regulated as a firearm under the Gun Control Act or the National Firearms Act".
Earlier this month, Sessions sent the changed machine gun definition to the Office of Management and Budget, continuing a process that began February 20 when Trump signed an executive order directing Sessions to get the ball rolling on a bump stock ban.