Republican Sens. Rand Paul, Mike Lee, and Ted Cruz have issued a letter to Senate Majority Leader Harry Reid stating that they plan to filibuster the gun-control legislation scheduled to hit the Senate floor next month.
"The 2nd Amendment to the Constitution protects citizens' rights to self-defense. It speaks to history's lesson that government cannot be in all places at all times, and history's warning about the oppression of a government that tries," the three senators write. "We will oppose the motion to proceed to any legislation that will serve as a vehicle for any additional gun restriction."
By opposing the motion to proceed, 60 votes would be required to advance the gun-control legislation, which includes universal background checks.
Aides say Paul, Lee and Cruz sent the letter to Reid now to make clear their intentions.
"Their goal was to put everyone on notice, since Reid has said he plans to take-up some sort of legislation on guns when we get back from recess," one aide said.
The White House on Tuesday said that a filibuster of the legislation would be "unfortunate."
Noting that public polling shows broad support for many of the gun safety proposals being discussed, White House spokesman Jay Carney added that the victims of gun violence "deserve" a vote.
"I don't think you could tell the families of those who have lost their children to gun violence that bills like this might be filibustered," Carney said. "I don't think that would be welcome news."
NBC's Shawna Thomas contributed to this report.