WASHINGTON — President Trump said Saturday that it would be up to states to decide whether to implement his controversial proposal to arm teachers, with the hope of deterring gunmen like the one who killed 17 people last week in South Florida.

In an afternoon tweet, Trump also claimed his idea would be “very inexpensive,” a notion that educators and others have disputed because of the training involved. Trump has said he envisions about 20 percent of teachers and other school personnel carrying weapons.

“Armed Educators (and trusted people who work within a school) love our students and will protect them,” the president said on Twitter. “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 has been pressing the notion for the past four days and has been more animated about the proposal than any other idea he has floated since the shooting at Marjory Stoneman Douglas High School in Parkland, Fla., on Feb. 14.

President Trump speaks at the Conservative Political Action Conference (CPAC) in National Harbor, Maryland, on Friday.

He and others in the administration have also talked about shoring up a federal database used in background checks for gun purchases, raising the age to purchase a semiautomatic rifle from 18 to 21 and banning bump stocks, a device makes a semiautomatic gun function like an automatic weapon.

The administration is also looking at using restraining orders to confiscate guns from mentally ill people or who otherwise raise “red flags.”

Earlier Saturday, Trump retweeted one of his tweets from two days ago that laid out his thinking.

“I will be strongly pushing Comprehensive Background Checks with an emphasis on Mental Health,” the president said. “Raise age to 21 and end sale of Bump Stocks! Congress is in a mood to finally do something on this issue – I hope!”

On Friday, Trump argued that the carnage in Parkland would have been less severe if teachers had been armed.

“A teacher would have shot the hell out of him before he knew what happened,” Trump said during an address to the Conservative Political Action Conference, an annual conclave of the American right, held just outside Washington.

The idea of arming teachers is supported by the National Rifle Association but opposed by the National Education Association, the country’s largest teachers lobby.