Donald Trump warns of civil unrest in US

Republican front-runner Donald Trump warned yesterday of riots if he is denied the party's presidential nomination after a string of primary election victories, raising the temperature even more in a heated White House race.

The outspoken billionaire New York businessman scored big wins in primaries in Florida, Illinois and North Carolina on Tuesday, knocking out rival Marco Rubio and bringing him closer to the 1 237 convention delegates he needs to win the nomination.

But Trump lost the crucial state of Ohio and left the door open for those in the party trying to stop him from becoming the Republican nominee for the November 8 election. Trump might fall short of the majority required, enabling the party's establishment to put forward another name at the July convention in Cleveland to formally pick its candidate.

In an interview with CNN yesterday, Trump said the party could not deny him the nomination should he fail to win enough delegates.

"I don't think you can say that we don't get it automatically. I think you'd have riots. I think you'd have riots. I'm representing many, many millions of people."

While the Republican race became mired deeper in turmoil, Hillary Clinton won victories in Florida, Illinois, Ohio and North Carolina on Tuesday that cast doubt on US Senator Bernie Sanders' ability to overtake her for the Democratic Party's nomination.

Republican Party leaders are appalled at Trump's incendiary rhetoric and believe his policy positions are out of step with core Republican sentiment, such as his vow to deport 11 million illegal immigrants, temporarily ban Muslims from the United States and build a wall along the border with Mexico.

Recent outbreaks of violence at Trump rallies have prompted President Barack Obama, a Democrat, and mainstream Republican figures to speak out against the real estate magnate.

In comments likely to raise more concern in the Republican establishment about Trump's lack of experience and temperament, the former reality TV show host said yesterday he was for the most part his own adviser on foreign affairs.

"I'm speaking with myself, number one, because I have a very good brain," he told MSNBC's "Morning Joe" show. "I know what I'm doing . . . My primary consultant is myself."

Trump also pulled out of the next televised Republican presidential debate, scheduled for Monday.

The Republican establishment's bid to stop Trump may have come too late as a field of candidates that once included him and 16 party figures has dwindled to only three with Trump (69), in command ahead of US Senator Ted Cruz (45) and Ohio Governor John Kasich (63), who won Ohio's Republican primary on Tuesday.

Trump's closest national challenger is Cruz, a Texan and favourite of the conservative Tea Party, who is second to Trump in delegates, but has struggled in states where conservative evangelical Christian voters, among Cruz's biggest supporters, are not dominant.

Cruz too warned of severe reactions against an attempt to stage a "brokered convention" in Cleveland and install a Republican candidate supported by party leaders.

"There are many in the Washington establishment that are having fevered dreams about a brokered convention, about a deadlocked convention where they parachute in an establishment candidate . . . I think that would be an absolute disaster. I think the people would quite rightly revolt," Cruz told CNN.

US House of Representatives Speaker Paul Ryan, a leading Republican, will not accept a nomination to be a presidential candidate, said his spokeswoman, AshLee Strong. Some party members have urged Ryan to step in.

"The speaker is grateful for the support, but he is not interested. He will not accept a nomination and believes our nominee should be someone who ran this year," Strong said in an email to Reuters.

Kasich, a former investment banker, is the last establishment Republican presidential candidate standing.