White House hopeful Donald Trump vowed Monday to "suspend immigration" from nations with links to terror attacks targeting the United States or its allies, one day after a Florida nightclub massacre.

"When I'm elected, I will suspend immigration from areas of the world where there is a proven history of terrorism against the United States, Europe or our allies, until we fully understand how to end these threats," Trump said during a national security speech in New Hampshire.

"We cannot continue to allow thousands upon thousands of people to pour into our country, many of whom have the same thought process as this savage killer."

Trump rapped his likely opponent in the US presidential race, Democrat Hillary Clinton, by saying she is pushing to expand immigration and the nation's refugee program to allow more Syrians into the United States.

"Clinton wants to allow radical Islamic terrorists to pour into our country. Immigration is a privilege, and we should not let anyone in this country who doesn't support our communities," he said.

Speaking of the Orlando shooter, who was born in New York to Afghan parents, Trump said "the killer was born an Afghan, of Afghan parents who immigrated to the United States,"

"The only reason the killer was in America in the first place was because we allowed his family to come here."

"We have a dysfunctional immigration system which does not permit us to know who we let into our country," he added.

Trump's blunt comments come six months after he controversially called for a ban on Muslims entering the United States.