President Donald Trump gestures to the media as he leaves the White House, Friday, Feb. 16, 2018, in Washington, for a trip to his private Mar-a-Lago resort in Florida.
President Donald Trump gestures to the media as he leaves the White House, Friday, Feb. 16, 2018, in Washington, for a trip to his private Mar-a-Lago resort in Florida.

U.S. President Donald Trump is supporting efforts to tighten federal background checks on gun buyers in the aftermath of last week's shooting of 17 people at a Florida high school, the White House said Monday. Trump's support comes amid a national outcry for legislative action to stem mass shootings. 

A Washington Post-ABC News poll released late Monday, 86 percent of respondents who identified themselves as Democrats said stricter gun control laws could have prevented the Florida shooting, while 67 percent of Republicans said stricter laws could not have prevented the massacre.

More than three-quarters of both groups said more effective mental health screening and treatment could have prevented the attack.

Overall, 77 percent of respondents said Congress is not doing enough to prevent mass shootings in the United States, while 62 percent said Trump was not doing enough.

White House press secretary Sarah Huckabee Sanders said Trump spoke last week with Texas Republican Senator John Cornyn about his bipartisan legislation with Connecticut Democratic Senator Chris Murphy, a long-time anti-gun advocate, to improve compliance with background checks. The revisions are still being negotiated.

Nikolas Cruz, the 19-year-old police say has confessed to gunning down 14 students and three adults at the Parkland, Florida, high school school he was expelled from last year, was able to buy an assault-style AR-15 rifle to carry out the mayhem after clearing a background check.

Cruz, wearing a red prison jump suit, appeared briefly in court Monday as lawyers discussed procedural issues in the premeditated murder case against him.

A video monitor shows school shooting suspect Niko
A video monitor shows school shooting suspect Nikolas Cruz (C) making an appearance before Judge Kim Theresa Mollica in Broward County Court, Thursday, Feb. 15, 2018, in Fort Lauderdale, Fla.

In Washington, Democratic lawmakers often call for tighter controls on gun purchases, while Republicans often oppose them, saying they would violate the Second Amendment to the U.S. Constitution that enshrines gun ownership. The Cornyn-Murphy legislation has drawn support from Democrats and Republicans, although passage of gun legislation has often stalled in the politically fractious Congress.

NRA support

The background check measure would not impose new restrictions on gun purchases, but rather attempt to make sure that information about mental health and criminal conviction records that legally bar individuals from buying weapons is consistently sent to the National Instant Criminal Background Check System.

In the recent past, U.S. authorities have frequently learned after someone has carried out a shooting rampage that they should not have been allowed to buy a weapon because of mental health issues or a criminal conviction, but the information was never forwarded to the national database

FILE - John Doll, of Renton, Wash., holds a sign t
FILE - John Doll, of Renton, Wash., holds a sign that reads "The people have the right to keep and bear arms" during a gun rights rally at the Capitol in Olympia, Wash.

Unlike many gun control proposals, the National Rifle Association, the dominant gun lobby in the U.S., supports improving the background check system. The legislation calls for a system of incentives and penalties to encourage government entities throughout the United States to report information about people with mental health issues or criminal backgrounds.

The FBI admitted it did not act on a tip on January 5 about Cruz when someone with a close relationship to him called in with information about the teenager’s "gun ownership, desire to kill people, erratic behavior and disturbing social media posts, as well as the potential of him conducting a school shooting."

Trump's support for improving the background check system came after the White House earlier said the president would hold what it called a "listening session" with high school students and teachers on Wednesday, although it did not give details.

Angelina Lazo, 18, center, a senior at Marjory Sto
Angelina Lazo, 18, center, a senior at Marjory Stoneman Douglas High School, holds a sign with other students and parents at an intersection near the Marjory Stoneman Douglas High School in Parkland, Fla.

Student demands

In Washington on Monday, several dozen students laid down on the street outside the White House in a protest, calling for tighter restrictions on gun sales.

Survivors of last week's massacre said they are planning a march on Washington and other major U.S. cities next month to demand tangible action from lawmakers to try to prevent future school shootings. Students are also going to Florida's state capital to meet with leaders on Wednesday, while Florida Governor Rick Scott is hosting workshops Tuesday on school security, mental health and gun safety.

Cameron Kasky said one of the reasons for the march is to pin "a badge of shame" on any politician who is accepting money from the National Rifle Association. She said the NRA is promoting a gun culture that leads to such horrors.

WATCH: Student protest in front of White House

Another student, Emma Gonzalez, told ABC that Trump, Florida Senator Marco Rubio, and Florida Governor Rick Scott all have NRA support. She said students "want to give them the opportunity to be on the right side of this." In an interview on CNN, she said, "If they accept this blood money, they are against the children ... you're either funding the killers, or you're standing with the children."

Sen. Marco Rubio, R-Fla., pauses as he speaks duri
FILE - Sen. Marco Rubio, R-Fla., pauses as he speaks during a news conference.

Meanwhile, Rubio, a Republican, threw his support Sunday behind a Democratic-sponsored state bill that would let courts allow police to seize guns from those who are determined to be a danger to others. Rubio told a Florida television station the law might have prevented the school massacre.

California already has such a law. But gun rights advocates oppose it, saying it would take away guns from those who are innocent of any crimes.

Several U.S. lawmakers are calling for stiffer background checks of gun buyers, but Congress has shown no inclination to stop the sale of assault weapons, even as national polls in the U.S. show widespread support among voters for such a ban.