Republican nominee Donald Trump becoming president of the United States would present a global danger, the top United Nations human rights official said today.

UN High Commissioner for Human Rights Zeid Ra'ad al Hussein cited Trump's views on vulnerable communities including minorities and his talk of using torture, banned under international law, as "deeply unsettling and disturbing".

"If Donald Trump is elected on the basis of what he has said already - and unless that changes - I think it is without any doubt that he would be dangerous from an international point of view," Zeid told a news briefing in Geneva.

Trump lashed out at US House Speaker Paul Ryan and other "disloyal" Republicans yesterday and vowed to campaign in whatever style he wants now that the party establishment has largely abandoned him. A 2005 video surfaced last week showing him bragging crudely to a reporter about groping women and making unwanted sexual advances.

A 2005 video surfaced last week showing him bragging crudely to a reporter about groping women and making unwanted sexual advances.Zeid, in a landmark speech in The Hague last month, accused Trump of spreading "humiliating racial and religious prejudice" and warned of a rise of populist politics that could turn violent.

Trump has been largely abandoned by the Republican Party. Photo: Reuters

"I always believe that it's incumbent on leaders to lead and to lead in a way that is ethical and moral," Zeid said, when asked about Trump.

"The use of half-truths is a very clever political device. Because as every propagandist knows, you allow the listener to fill in the rest."

Trump, 70, has portrayed himself as tough on national security and vowed to built a wall to stop Mexican immigrant "rapists" from crossing the border.

"We have to be on guard to see that in the end vulnerable populations, populations at risk do not again see their rights deprived because of a view that is in the ascendancy based on false premises," Zeid said.