Republican presidential nominee Donald Trump is a "unique and present danger" to the Constitution and his presidency will be dangerous not only to the United States, but also to the world, The Washington Post said Sunday.

In an unusually lengthy editorial, the newspaper lambasted the real-estate tycoon for lacking experience and being ignorant yet refusing to learn, unspooling one lie after another, flip-flopping on key issues, and offering only prejudices and gut feelings, most of them erroneous, to problems.

Referring to Trump's insistence that allies are taking advantage of the U.S. and American troops should be withdrawn unless the allies pay more, the paper said that South Korea and Japan "are major contributors to an alliance that has preserved a peace of enormous benefit to Americans."

"Donald J. Trump, until now a Republican problem, this week became a challenge the nation must confront and overcome. The real estate tycoon is uniquely unqualified to serve as president, in experience and temperament. He is mounting a campaign of snarl and sneer, not substance," the Post said.

"A Trump presidency would be dangerous for the nation and the world," it said.

Trump's lack of electoral experience might be overcome if he saw it as a handicap worth overcoming, but he "displays no curiosity, reads no books and appears to believe he needs no advice," the paper said, adding that the nominee has made a series of lies about key issues and refuses to correct them even when faced with evidence.

"Existing trade deals are 'stupid,' but Mr. Trump does not say how they could be improved. The Islamic State must be destroyed, but the candidate offers no strategy for doing so. Eleven million undocumented immigrants must be deported, but Mr. Trump does not tell us how he would accomplish this legally or practically," the paper said.

"What the candidate does offer is a series of prejudices and gut feelings, most of them erroneous. Allies are taking advantage of the United States. Immigrants are committing crimes and stealing jobs. Muslims hate America. In fact, Japan and South Korea are major contributors to an alliance that has preserved a peace of enormous benefit to Americans," it said.

It also blasted Trump for his willingness to abandon NATO, encouraging more nations to obtain nuclear weapons and cozying up to dictators. Trump has also made clear that he would "drop allies without a second thought" and its consequences to global security could be "disastrous," the paper said.

"Many Americans do not like either candidate this year. We have criticized the presumptive Democratic nominee, Hillary Clinton, in the past and will do so again when warranted. But we do not believe that she, (or the Libertarian and Green Party candidates, for that matter) represents a threat to the Constitution," the paper said.

"Mr. Trump is a unique and present danger."  (Yonhap)