Donald Trump defended the National Rifle Association, Americans biggest gun lobby, saying it was led by "great people" who would "do the right thing".
The US president reiterated his support for arming some teachers in schools in response to one of America's worst high school shootings, in Florida last week.
Writing on Twitter, Trump said: "What many people don't understand is that the folks who work so hard at the NRA are Great People and Great American Patriots. They love our country and will do the right thing."
He added: "If a potential 'sicko shooter' knows that a school has a large number of very weapons talented teachers and others who will be instantly shooting, the sicko will NEVER attack that school.
"Cowards won't go there...problem solved. Must be offensive, defensive alone won't work! Highly trained teachers would also serve as a deterrent to the cowards that do this. ATTACKS WOULD END!"
Trump said he wanted to see action on gun control measures also including tightening background checks for buyers, investment in mental health, and banning "bump stock" devices that increase a gun's rate of fire.
He is also looking at raising the age people can buy a semi-automatic weapon from 18 to 21.
Trump said: "Congress is in a mood to finally do something on this issue - I hope! I will be strongly pushing Comprehensive Background Checks with an emphasis on Mental Health. Raise age to 21 and end sale of Bump Stocks!"
Alfonso Calderon, 16, a survivor of the Florida shooting, rejected the idea of arming teachers.
He said: "I don't know if Donald Trump has ever been to a public high school, but as far as I'm aware, teachers are meant to be educators.
"They're meant to teach young minds how to work in the real world. They are not meant to know how to carry AR-15s. They are not meant to know how to put on Kevlar vests for the other students or themselves."
Wayne LaPierre, the executive vice president of the National Rifle Association, issued a full-throated statement of support for Trump's proposal.
Speaking at the Conservative Political Action Conference (Cpac), LaPierre questioned the "bizarre" fact that NBA games and parts of Hollywood are protected by armed guards but schools are not.
"Do we really love our money and our celebrities more than we love our children?" he asked.
He added: "Evil walks among us and God help us if we don't harden our schools and protect our kids."
LaPierre also said: "If armed security makes us less safe let's remove it from the White House and all of Hollywood."
He criticised the "breathless" national media for calling for gun control after the Florida school shooting and criticised the instinct to demand more laws after such tragedies.
LaPierre said: "We must immediately harden our schools. Every day young children are being dropped off at schools that are virtually wide-open soft targets for anyone bent on mass murder.
"It should not be easier for a madman to shoot up a school than a bank or a jewellery school or some Hollywood gala.
"Schools must be the most hardened targets in this country and evil must be confronted immediately with all necessary force to protect our kids."
However Marco Rubio, the Republican senator from Florida and supporter of the NRA, publicly criticised Trump's plan in a town hall debate on CNN.
He said the idea had "practical problems" and questioned how he would feel as a parent if his children attended schools with armed teachers.
Rubio said of arming teachers: "I don't support that, and I would admit to you right now I answer that as much as a father as I do as a senator.
"The notion that my kids are going to school with teachers that are armed with a weapon is not something that, quite frankly, I'm comfortable with."