I won't defend Donald Trump

Paul Ryan, the top Republican in the US Congress, took the extraordinary step on Monday of distancing himself from Donald Trump, stirring a backlash from some lawmakers and deepening a crisis over his party's struggling presidential nominee.

In a conference call with congressional Republicans, Ryan all but conceded that Democrat Hillary Clinton was likely to win the White House on Nov 8 and said he would put his full energy into preserving Republican majorities in Congress so as not to give her a "blank check."

Ryan, the speaker of the House of Representatives, said he would not defend Trump or campaign for him after the uproar over the New York businessman's sexually aggressive comments that surfaced on Friday.

Ryan's announcement added to the party's worst turmoil in decades and reinforced the growing sense of isolation around Trump, who has never previously run for public office.

Trump hit back at Ryan, the Republican vice presidential candidate in 2012, who has frequently been critical of him.

"Paul Ryan should spend more time on balancing the budget, jobs and illegal immigration and not waste his time on fighting Republican nominee," Trump wrote on Twitter.