President Donald Trump enthusiastically embraced the National Rifle Association on Friday, vowing not to tighten U.S. firearms laws, despite suggesting just weeks ago after a Florida school shooting that he would take on the powerful gun-rights group.

At the NRA's annual convention in Dallas, Trump called again for arming teachers and increasing school security to head off future mass shootings like the one in Parkland, Florida, that killed 17 people. Such measures are supported by the NRA.

With Republican control of the U.S. Congress up for grabs in November's midterm elections, Trump used the NRA platform to return to rhetoric he used in 2016 to excite pro-gun voters, warning that Democrats are determined to take away Americans' guns.

Trump made no mention of gun-control proposals he tentatively floated in the past, such as raising the age limit for buying rifles. The NRA opposes that and other limits on gun sales as a violation of the right to gun ownership under the Second Amendment to the U.S. Constitution.

Democratic lawmakers generally support tighter gun laws, but specific proposals that they favor, such as universal background checks and a ban on military-style "assault" rifles, would not alter the Second Amendment.

The Parkland massacre at Marjory Stoneman Douglas High School on Feb. 14 seemed to mark a turning point in America's long-running gun debate.

Days after the shooting, Trump promised action on gun regulation and said of the NRA: "We have to fight them every once in a while."

But since then, no major new federal gun controls have been imposed.