The National Rifle Association pushed back on Sunday against modest proposals by President Donald Trump and other Republicans to change U.S. gun laws after a school shooting in Florida that killed 17 students and staff.

The powerful gun lobby group does not support Trump's proposals to raise the age limit for buying certain types of guns or to ban bump stocks that enable semi-automatic rifles to shoot hundreds of rounds a minute, a spokeswoman said on ABC's "This Week."

"The NRA doesn't back any ban," Dana Loesch said.

Trump was endorsed by the NRA in his 2016 presidential election campaign and often trumpets his support for Americans' constitutional right to own guns.

But the February 14 massacre at a Florida high school has mobilised high school students to push for restrictions on gun sales, spurred several companies to sever ties with the NRA and energised gun-control activists.