President Joe Biden has appealed for the country to "unite as one nation" after Saturday's apparent attempted assassination of former President Donald Trump and said he was ordering an independent security review of the lead-up to the attack.

Biden delivered brief remarks from the White House on Sunday after receiving a briefing on the investigation in the Situation Room. He said he has directed the probe to be "thorough and swift," and asked the country not to "make assumptions" about the perpetrator's motives or affiliations.

Biden plans to deliver extended remarks to the nation Sunday evening in a prime-time address from the Oval Office.