President Donald Trump speaks about the mass shooting at a Florida high school in a national address from the White House in Washington, U.S., February 15, 2018.

President Donald Trump appeared Saturday to begin refining his proposals for combatting school violence, tweeting that arming teachers as a deterrent against such often deadly violence — an idea he championed in recent days — is "Up to States."

Trump heavily promoted the idea of putting "gun-adept" teachers and staff carrying concealed firearms in classrooms and schools to protect students following this month's shooting at Marjory Stoneman Douglas High School in Parkland, Florida, that killed 17 people, most of them students.

He called for bonuses for educators who volunteer to carry a firearm, and said he also wanted action to strengthen background checks and boost the minimum age for the purchase of assault-style weapons.

Expectations were raised that Trump would propose federal legislation on arming teachers, but that no longer appeared to be the case Saturday.

"Armed Educators (and trusted people who work within a school) love our students and will protect them. Very smart people. Must be firearms adept & have annual training. Should get yearly bonus. Shootings will not happen again - a big & very inexpensive deterrent. Up to States," Trump tweeted.

Donald Trump tweet

The White House did not immediately respond to a request for comment about the president's tweet.

The White House has yet to offer a complete plan to address school violence amid the public outcry sparked by the Florida shooting, including addressing who would bear the financial cost. Trump said in the tweet that arming educators and paying their bonuses would be "very inexpensive."

Asked on Thursday whether the federal government or state and local municipalities would pay the millions of dollars it would cost to train and arm teachers, White House spokesman Raj Shah said "the policy hasn't been fleshed out," adding "Do we really think that that's too much to pay for school safety?"

Teachers and law enforcement organizations oppose the idea, while several states are considering arming teachers.

Trump spent several days earlier this week hearing emotional pleas from parents and students, including some who survived the Parkland shooting, and others who had lost children in school shootings in Connecticut and Colorado. He also solicited input from state and local officials.

Trump and Vice President Mike Pence have said school safety will be a top agenda item when they meet with the nation's governors next week.