Biden insisted he had a "good night" in Iowa even as he trailed the top moderate candidate, former Mayor Pete Buttigieg of South Bend, Indiana, and the leading progressive, Bernie Sanders, according to initial returns from 62 per cent of precincts.

The results followed 24 hours of chaos as technical issues marred the contest, forcing state officials to apologize and raising questions about Iowa's traditional place atop the presidential primary calendar.

Speaking in Iowa hours ahead of U.S. President Donald Trump, Democratic presidential hopeful Joe Biden ripped the Republican president's trade policies, saying that farmers were being caught in the crossfire between the United States and China.