US intelligence agencies have briefed former president Donald Trump on the "real and specific" threat to his life allegedly from Iran to allegedly "sow chaos" in the country, according to his campaign.

Two apparent assassination attempts have been made in the same number of months on the life of the 78-year-old Republican presidential candidate.

“President Trump was briefed earlier today by the Office of the Director of National Intelligence regarding real and specific threats from Iran to assassinate him in an effort to destabilise and sow chaos in the United States,” Steven Cheung, Trump's Campaign communications director said late Tuesday night.

Intelligence officials have identified these "continued and coordinated" attacks heightened in the past few months, and law enforcement officials across all agencies are working to ensure Trump is protected and the November election is free from interference, Cheung said.

On July 13, the first failed assassination attempt on Trump was made during a rally in Butler, Pennsylvania, when a bullet grazed his ear. The second bid on his life took place on September 15 at the Trump International Golf Club in West Palm Beach, Florida.

Fifty-eight-year-old Ryan Wesley Routh, who was spotted with a gun outside the golf course, was officially charged on Tuesday for attempting to assassinate a major presidential candidate.

"Make no mistake, the terror regime in Iran loves the weakness of Kamala Harris and is terrified of the strength and resolve of President Trump. He will let nothing stop him or get in his way to fight for the American people and to Make America Great Again," he said.

The presidential elections will take place in the US on November 5, when Trump will face Democratic Party presidential candidate Vice President Kamala Harris.