US President Donald Trump reiterated his strong support for gun rights and commitment for mid-term elections during a speech in the Texas city of Dallas.

"Your Second Amendment rights are under siege but they will never ever be under siege as long as I am your president. We cannot get complacent. We have to win the mid-terms," Trump said at the National Rifles Association (NRA) annual meeting in the convention center in Dallas.

During his speech, Trump didn't mention the Florida school rampage a few months ago that killed 17 people, but focusing on the common ground he shares with gun owners who helped deliver the election to him, and whose support Republicans need in November's mid-term elections.

Trump pushed the point by citing a hospital in London, where firearms are illegal but violence still erupts as criminals turn to knives.

"There's blood all over the floors of this hospital," he said. "Knives, knives, knives."

Before Trump, Vice President Mike Pence also reassure NRA members of gun rights.

"You have two friends in the White House. President Donald Trump and I both stand without apology for the Second Amendment and in this administration the right of the people to keep and bear arms will not be infringed," Pence told the crowd.

Meanwhile, gun control advocates accused Trump of bending his knee to the NRA instead of working to curb gun violence.

"It's the job of the president to ensure our public safety, but Trump takes his marching orders from the NRA," Gabby Giffords, the former Arizona congresswoman who was badly wounded in a shooting, said in a statement. "Trump has ignored the pleas of young people demanding safer gun laws."