Trump on the ban on 12 countries: We don't want them

US President Donald Trump has said that the recent attack in Boulder, Colorado, where 12 people were injured when a man attacked a group gathered in support of the Israeli hostages, highlights the extreme risks posed to the US by the entry of foreign nationals without proper vetting, as well as those who come as temporary visitors and overstay their visas.

"We don't want them," Trump said, adding that he believes the US cannot have "open migration to any country where it cannot safely and reliably vet and control those seeking entry."

"The strength of these new restrictions applied depends on the severity of the threat presented," Trump continued.

He added that the list of countries under ban is "subject to review" if improvements are made.