'Cool it down,' Biden tells nation after Trump assassination bid

WASHINGTON - President Joe Biden sought to calm a divided nation after his rival Donald Trump survived an assassination bid, saying in a rare Oval Office address Sunday it was time to lower the temperature of America's hostile politics.

"You know, the political record in this country has gotten very heated. It's time to cool it down," Biden said in the televised speech, just the third he has given from behind the historic Resolute Desk during his presidency.

As the country reeled from images of a bloodied Trump waving his fist after a gunman opened fire at a rally in Pennsylvania, Biden added that US politics "must never be a literal battlefield, a, God forbid, a killing field."

The 81-year-old Democrat said that both sides had a responsibility to ease the situation ahead of a deeply polarized election that would now be a "time of testing" for the United States.

The short but forceful speech went without any major hitches -- bar Biden twice referring to the ballot box as a "battle box" -- with the ageing president under close scrutiny following a disastrous debate performance against Trump recently.

Investigators said that they were still probing the motives of 20-year-old gunman Thomas Matthew Crooks, who was shot dead by snipers at the event in Butler, Pennsylvania, on Saturday after firing multiple shots with a legally-bought semi-automatic rifle.

Former president Trump said on social media Sunday that Americans should not allow "evil to win," adding it was "more important than ever that we stand United."

The 78-year-old Republican later added on social media that it was "God alone" who had saved him. Trump's wife Melania called the shooter a "monster."

The attempt on Trump's life sent shock waves around the world, but the effects on a tight US presidential race in a deeply divided country are uncertain.

US politics have become increasingly hostile, with Trump building his image around inflammatory verbal assaults, and many Democrats expressing fury and disgust at Trump's rise.