WASHINGTON — President Trump endorsed stricter gun-control measures Thursday, including raising the minimum age to 21 for possessing a broader range of weapons than at present. He tweeted his strongest stance as president one day after an emotional White House session where students and parents poured out wrenching tales of lost lives and pleaded for action.

Trump said on Twitter, “I will be strongly pushing Comprehensive Background Checks with an emphasis on Mental Health. Raise age to 21 and end sale of Bump Stocks!” The president did not immediately offer more details.

Trump’s focus on gun violence came as leaders of the National Rifle Association offered a vigorous defense of gun rights during the Conservative Political Action Conference, urging enhanced – and armed – security at schools.

“Evil walks among us and God help us if we don’t harden our schools and protect our kids,” said NRA Executive Vice President and CEO Wayne LaPierre. “The whole idea from some of our opponents that armed security makes us less safe is completely ridiculous.”

This AR-15 is similar to the one Nikolas Cruz legally purchased about a year before last week’s mass shooting in Parkland, Florida.

The NRA officials didn’t address whether the federal government should raise the age limit for young adults to buy weapons, accusing Democrats and media outlets of exploiting the Florida shooting.

“Many in legacy media love mass shootings, you guys love it,” said NRA spokeswoman Dana Loesch at CPAC. “Now I’m not saying that you love the tragedy, but I am saying that you love the ratings. Crying white mothers are ratings gold.”

The current federal minimum age for buying or possessing handguns is 21, but the limit is 18 for rifles including assault-type weapons such as the AR-15 used by a former student in last week’s attack on a Florida high school that killed 17 students and staff members.

A White House official said the president was not endorsing or ruling out any specific policy.

In another tweet, Trump repeated his urgent call for trained teachers or others in schools to carry guns as a deterrent to attacks.

“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, defense alone won’t work!” Trump tweeted.

He has previously expressed an interest in efforts to strengthen the federal background check system. It was not clear if he would back closing loopholes that permit loose private sales on the internet and at gun shows.

The National Rifle Associated on Wednesday quickly rejected any talk of raising the age for buying long guns to 21.

“Legislative proposals that prevent law-abiding adults aged 18-20 years old from acquiring rifles and shotguns effectively prohibits them for purchasing any firearm, thus depriving them of their constitutional right to self-protection,” the group said in a statement.

Trump, despite his new push for at least some gun-control changes, stressed his backing for the NRA on Thursday, tweeting 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. MAKE AMERICA GREAT AGAIN!”

On Wednesday, Trump listened intently at the White House as students described the horror of the shootings at Marjory Stoneman Douglas High School in Parkland Florida. The students and their parents appealed to him to press for stricter gun controls.

“I turned 18 the day after” the shooting, said tearful student Samuel Zeif. “Woke up to the news that my best friend was gone. And I don’t understand why I can still go in a store and buy a weapon of war. An AR. How is it that easy to buy this type of weapon? How do we not stop this after Columbine? After Sandy Hook?”

Trump promised to be “very strong on background checks.” And he indicated he supported allowing some teachers and other school employees to carry concealed weapons to be ready for intruders.

The president had invited the teen survivors of school violence and parents of murdered children in a show of his resolve against gun violence in the wake of last week’s shootings in Florida and in past years at schools in Connecticut and Colorado.

Trump asked his guests to suggest solutions and solicited feedback. He did not fully endorse any specific policy solution, but pledged to take action and expressed interest in widely differing approaches.

He largely listened, holding handwritten notes bearing his message to the families. “I hear you” was written in black marker.

Besides considering concealed carrying of weapons by trained school employees, a concept he has endorsed in the past, he said he planned to go “very strongly into age, age of purchase.” And he said he was committed to improving background checks and working on mental health.

Most in the group Wednesday were emotional but quiet and polite.

But Andrew Pollack, whose daughter Meadow was killed last week, noted the previous school massacres and raged over his loss, saying this moment isn’t about gun laws but about fixing the schools.

“It should have been one school shooting and we should have fixed it and I’m pissed. Because my daughter, I’m not going to see again,” said Pollack. “King David Cemetery, that is where I go to see my kid now.”

A strong supporter of gun rights, Trump has nonetheless indicated in recent days that he is willing to consider ideas not in keeping with National Rifle Association orthodoxy, including age restrictions for buying assault-type weapons. Still, gun owners are a key part of his base of supporters.

The people assembled for the White House meeting on Wednesday included parents of students killed in massacres at Columbine High School in Littleton, Colorado, and Sandy Hook Elementary in Newtown, Connecticut. Students and parents from the Washington area also were present.

Trump later tweeted that he would “always remember” the meeting. “So much love in the midst of so much pain. We must not let them down. We must keep our children safe!!”

The AP’s Zeke Miller, Jill Colvin, Ken Thomas, Sadie Gurman, Marc Levy and Alina Hartounian contributed to this story.