WASHINGTON (BLOOMBERG) - President Donald Trump directed the Justice Department to write regulations banning the use of accessories known as "bump stocks" that allow semiautomatic rifles to be fired more rapidly, and his press secretary declined to rule out supporting restrictions on the purchase of AR-15-style rifles like the one used in a Florida school shooting last week.

"I signed a memorandum directing the attorney-general to propose regulations to ban all devices that turn legal weapons into machine guns," Trump said on Tuesday (Feb 20) at the White House.

"I expect that these critical regulations will be finalised, Jeff, very soon," he added, speaking to Attorney-General Jeff Sessions.

He added that the government should focus on "evidence-based solutions" to gun violence.

Asked if Trump would support renewing a federal assault weapons ban that expired more than a decade ago, White House Press Secretary Sarah Sanders said at a briefing that "we haven't closed the door on any front."

She also said it "hasn't yet been determined" whether there should be a federal age limit for purchasing semiautomatic rifles like the one the Florida shooter bought as a teenager.

"Background checks are something that the president is supportive of making more efficient and looking at better ways to improve that process," Sanders said.

Her briefing was the White House's first since the attack at Marjory Stoneman Douglas High School in Parkland, Florida, which killed 17 people and reignited calls for stricter gun controls.

A group of students from the school traveled on Tuesday to Tallahassee, the state capital, to call for a ban on AR-15-style rifles like that used in the attack.

Students from the school are also planning a march on Washington on March 24.

Trump will meet with parents, students and teachers who survived earlier shootings tomorrow and with police later this week to discuss the Feb 14 attack, Sanders said.

He will also discuss gun laws next week with governors.

The President wants to "make sure we're doing everything we can from every capacity, the state, federal and local level, to make sure incidents like this don't happen again," she said.

The suspect in the attack, 19-year-old Nikolas Cruz, killed 17 people in six minutes using an AR-15-style rifle that he had purchased legally.

Trump spoke to Texas Republican Senator John Cornyn on Friday about a bill he proposed last year with Connecticut Senator Chris Murphy, a Democrat, that would strengthen the current background check system for gun purchases.

The legislation aims to put more pressure on federal agencies to report relevant information to the National Instant Criminal Background Check System and also includes measures to reward states that comply with the system through federal grants. The National Rifle Association has expressed support for the legislation.

Trump on Friday visited a hospital where many of the shooting victims were treated, as well as the headquarters of the Broward County Sheriff's Department.

At the hospital, he spoke with a few of the victims and said it was "very sad something like that could happen".

He also praised emergency workers for rapidly responding to the attack.

"We must move past cliches and tired debates and focus on evidence-based solutions and security measures that actually work and that make it easier for men and women of law enforcement to protect our children and to protect our safety," Trump said on Tuesday.