Donald Trump will return to the site of the first assassination attempt against him, as an inquiry uncovers “dire failures” by the Secret Service in protecting the former president.

Trump’s campaign said he will hold a rally at Butler, Pennsylvania — the town where he escaped with only a grazed ear when a gunman fired at him on stage in July – on October 5.

“President Trump’s return to Butler will mark his first visit to the site of the attack since he was struck by an assassin’s bullet on July 13th – but was saved in what the world has recognised as an act of divine providence,” his campaign said in a statement.

Trump would honour the memory of fireman Corey Comperatore, who was killed in the assassination attempt, the campaign said.

Pennsylvania is one of a handful of key states that are expected to decide the November 5 election. Latest polls have Trump’s Democratic rival, Kamala Harris, slightly ahead in the state – but only by a result within polls’ margin of error.

Wednesday’s announcement came as a bipartisan US Senate investigation found multiple failures of the Secret Service ahead of the rally that were “foreseeable, preventable and directly related to the events resulting in the assassination attempt that day”.

The Senate Homeland Security and Governmental Affairs Committee’s interim report released on Wednesday (US time) found failures on almost every level, including in planning, communications, security and allocation of resources.

“The consequences of those failures were dire,” the Democratic chairman of the Homeland panel, Michigan senator Gary Peters said.

Investigators found there was no clear chain of command among the Secret Service and other security agencies and no plan to cover the building that a gunman scaled to fire the shots.

Officials were operating on multiple, separate radio channels, leading to missed communications, and an inexperienced drone operator was stuck on a helpline after his equipment was not working correctly.

Communications among security officials were a “multistep game of telephone”, Peters said.

The report found the Secret Service was notified about an individual on the roof of the building approximately two minutes before gunman Thomas Matthew Crooks opened fire, firing eight rounds in Trump’s direction just 137 metres from where the former president was speaking.

Trump, the 2024 Republican US presidential nominee, was struck in the ear by a bullet or a bullet fragment in the assassination attempt, Comperatore was killed and two other rally goers were injured before Crooks was killed by a Secret Service counter-sniper.

About 22 seconds before Crooks fired, the report found, a local officer sent a radio alert of an armed individual on the building.

But that information was not relayed to key Secret Service personnel who were interviewed by Senate investigators.

The panel also interviewed a Secret Service counter-sniper who said that they saw officers with their guns drawn running toward the building where the gunman was perched. That person said they did not think to notify anyone to get Trump off the stage.

On Thursday, Australia’s former ambassador to the US, Joe Hockey, accused the Secret Service of a “serious failure”.

It would have been the “greatest risk … to civil society of recent times” if the assassin’s bullet had “taken [Trump] out”, he said.

“Everyone saw graphically how close it was and it was a failure by the Secret Service, I mean a really serious failure,” he said on ABC’s TV’s Meet the Press.

The Senate report comes just days after the Secret Service released a five-page document summarising the key conclusions of a yet-to-be finalised report on what went wrong in Butler, and ahead of a Thursday hearing by the bipartisan House task force investigating the shooting.

The house panel is also investigating a second assassination attempt on Trump earlier in September when Secret Service agents arrested Ryan Routh. He was allegedly hiding with a gun on the golf course at Trump’s Florida club.

-with AAP