US President Joe Biden says the United States is being reminded every day that “nothing is guaranteed” about its democracy after six people were killed and 24 hospitalized after a mass shooting.

The Highland Park Independence Day parade was halted after 10 minutes when gunshots rang out through the crowd.

“There is nothing guaranteed about our way of life – we have to fight for it, defend it and earn it by voting to refine, evolve and expand,” he said.

“This day reminds us of what brought us together long ago. What still binds us and, at our best, what we strive for.”