CANBERRA, Australia — Australia’s deputy prime minister warned Friday that the greatest threat to the US economy is the ‘‘cranks and crazies’’ in the Republican Party, a rare foray into American domestic politics that was blasted by the opposition.

Wayne Swan, who also is treasurer and his center-left Labor Party government’s ranking finance minister, took aim at the Tea Party during a speech to a business forum, breaking a convention among Australia’s major parties to steer clear of US domestic political debates.

He said ‘‘the extreme right Tea Party wing’’ of the Republican Party had held the national interest hostage during last year’s debate over the US borrowing limit , despite President Obama’s ‘‘good will and strong efforts.’’

He said it was imperative that Congress reach an agreement to support growth and avoid a ‘‘fiscal cliff’’ of deep government spending cuts and higher taxes in January, which he said could push the US economy back into recession.