BERLIN (Reuters) - Germany's economy ministry believes a Donald Trump presidency would severely damage the US economy, according to an internal memorandum reported by Der Spiegel magazine on Saturday (Oct 1).

The ministry expects "shrinking gross domestic product, fewer jobs and higher unemployment," in the United States if the Republican candidate were to implement his campaign pledges, the magazine cited the memo as saying.

Trump, a billionaire businessman seeking his first public office, has proposed tax cuts worth $4.4 trillion (S$6 trillion) and wants to curb government regulation and take a tougher stance on negotiating trade deals.

He says his economic plan would produce annual economic growth of 3.5 per cent and create 25 million jobs over a decade. But some economists have questioned the assumptions underpinning the plan.

Trump's pledges are "not feasible", Spiegel cited the memorandum as saying. Moreover, the plans would violate international or US law and could be "no basis for a realistic economic policy." A spokeswoman for the German Economy Ministry declined to comment on the Spiegel report.

Last month, economic research firm Oxford Economics projected the US economy could be $1 trillion smaller than otherwise expected in 2021 if Trump becomes president.

Trump faces Democrat Hillary Clinton in the Nov 8 election.