Former defence minister Kim Beazley has warned a Donald Trump presidency could cause mayhem for Australia's national security and wreck the crucial security alliance with the United States.

Key points: Beazley says Trump would "trash" trade and alliance relations

Beazley says Trump would "trash" trade and alliance relations Beazley urges Australia to "confront" Trump and demand change

Beazley urges Australia to "confront" Trump and demand change US security officials warn Trump would be "most reckless president"

His comments come after senior national security officials in the US warned Mr Trump would be the most reckless president in American history.

Mr Beazley — who finished his posting as US ambassador earlier this year — told the ABC the Republican candidate would also trigger an unnecessary confrontation with China if he wins the election.

"Were there to be a Trump presidency — and I think that's slightly less likely than more likely that that will occur — he would trash basically the structure of alliance relationships and trade relationships in our immediate region," he said.

"That would affect in a major way some of our most important trading partners and it would destabilise enormously the relationship we have in the north part of Asia."

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Mr Beazley said a Trump presidency would present a serious challenge for Australia, putting the Government in a position where it would have to "wean him away from the lunacy".

He said Australia would have the unique opportunity "to confront a Trump presidency and demand they listen and demand they change".

His comments follow the most recent concerns over Mr Trump, who has suggested that "Second Amendment people" — gun owners or those backing gun rights — could stop Hillary Clinton from winning the White House and picking new US Supreme Court justices.

"Hillary wants to essentially abolish the Second Amendment," Mr Trump told a rally in Wilmington, North Carolina, referring to the US Constitution's clause that enshrines the rights of Americans to bear arms.

"If she gets to pick her judges, nothing you can do folks," Mr Trump said. "Although the Second Amendment people — maybe there is, I don't know."

The Trump campaign swiftly issued its own statement to clarify the brash billionaire's remarks, branding the media as "dishonest" and saying he meant that gun rights advocates were a powerful voting force.

The Secret Service has said it is "aware of the comments".