"We have to do something about it. We have to act," Trump said, voicing support for expanded background checks, more secure schools, curbs on the ability of the mentally ill to buy firearms and raising to 21 the age for buying certain guns.
"We can't wait and play games and nothing gets done," Trump said at a meeting with lawmakers from both parties.
At one point, he turned to a Republican senator and said: "You're afraid of the NRA," referring to the National Rifle Association, the premier and powerful US gun lobby.
With tears, fears and defiance, students also made an emotional return Wednesday to their Florida high school where a former classmate went on a shooting rampage two weeks ago, killing 17 people.
More From This Section
Students at Marjory Stoneman Douglas High School in Parkland were greeted by heavy security and scores of well-wishers as they returned to classes.
Dozens of police officers lined the sidewalks saying "Good morning" to each child and retired officers passed out flowers. Former students, neighbors and their children held banners reading "We Love You," "You've Got This" and "We Are With You."
"It was just sad to go back there and not have my friends who were in the class with me anymore."
Likewise, for Kimberly Miller, the first day back meant confronting the absence of her geography teacher, 35-year-old Scott Beigel.
Beigel was one of three staff killed, along with 14 teenagers, when former student Nikolas Cruz entered the school on Valentine's Day and opened fire with a semi-automatic rifle.
"It's pretty upsetting," said the 14-year-old Miller. "But it was also refreshing to talk to everyone because people don't really understand how it feels, no matter how much they try to understand."
Jonathan Abramchaev, 15, said it was "very emotional" to see his school again.
"Seeing all the flowers by the gate, that really hurt me," he told AFP. "Today we were just discussing and talking out our feelings."
Some said they felt reassured -- if a little unsettled -- by the heavy police presence.
"I'm not scared," said Stoneman Douglas junior Sean Cummings. "I feel like it's more protected than any other school at this point.
"But it's still weird to see everybody here and all these police officers," said the 16-year-old.
"I'm really scared to go in," said Novell, who like many others wore a maroon T-shirt, the school colors.
Broward County school superintendent Robert Runcie said grief counselors were on hand for the day.
"We're going to provide as much support as we can," Runcie told CNN. "Students are excited. As a family, they're going to pull through it."
A 15-year-old named Alan said the shooting left him fearful -- even with his school under close watch by police.
"What happens when they go? In a couple of days or weeks when it gets back to normal? It may happen again," he said.
Republican lawmakers, with majorities in the US Congress and the Florida state legislature, have been cool on bringing in major reforms on the sales of firearms.
But Trump upped the pressure on lawmakers to get to work, hosting the bipartisan meeting at the White House where he raised eyebrows with his tough stance.