Republican Ted Cruz has won the Wisconsin presidential primary, dealing a blow to frontrunner Donald Trump’s hopes of amassing the delegates needed for the party’s nomination ahead of the July convention and boosting the chances of a rare contested convention.

Mr Cruz’s win was a breakthrough for Republican Party forces battling to block the controversial New York billionaire, and raised the prospect of a prolonged nominating fight that could last to the July convention.

Democratic presidential contender Bernie Sanders also won in Wisconsin, gaining momentum in his fight against frontrunner Hillary Clinton and trimming her commanding lead in delegates.

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Mr Trump had 737 convention delegates to Mr Cruz’s 481 heading into the vote, leaving him 500 delegates short of the 1,237 needed to win the nomination.

The hardworking men and women of Wisconsin stood and campaigned tirelessly to make sure that tonight was a victory for every American,” Mr Cruz said after his victory.

“We have a choice. A real choice. The national political terrain began to change two weeks ago.

“In the state of Utah, we won 69 per cent of the vote, a landslide election.”

Mr Cruz and Ohio Governor John Kasich, the other remaining Republican contender, hope to stop Mr Trump short of a first-ballot victory and trigger a contested convention.

Mr Cruz, a conservative US Senator from Texas, was aided in Wisconsin by the backing of Republican Governor Scott Walker, who had dropped his own presidential bid in September.

Party establishment bands together behind Cruz

Party establishment figures, worried that Mr Trump will lead Republicans to a broad defeat in November, have banded together to try to stop him.

The Wisconsin primary followed a difficult week for Trump, who was forced to backtrack after saying women who have abortions should face punishment if the procedure is outlawed, and who voiced support for his campaign manager after he was charged with misdemeanour assault for grabbing a reporter.

A new Reuters/Ipsos poll released on Tuesday showed Mr Cruz about even with Mr Trump nationally, with Mr Cruz’s recent gains the first time since November that a Trump rival has threatened his standing at the head of the Republican pack.

In the Democratic race, the win for Mr Sanders, a US Senator from Vermont, is his sixth in the last seven presidential nominating contests, but he still faces a difficult task to overtake Mrs Clinton as the presidential nominating race moves to New York on April 19 and to five other Eastern states on April 26.

Mrs Clinton will head into New York with confidence, currently holding a double digit lead over Mr Sanders.

Good luck with that’: Obama ridicules Trump plan

After a week of headlines focused on his missteps and his lag in Wisconsin polls, Mr Trump turned to illegal immigration as a cornerstone of his campaign that is popular with his supporters.

President Obama dismissed the money transfer freeze as “not thought through”. Photo: ABC

The New York billionaire has drawn strong criticism for his harsh rhetoric on Muslims, women and immigration — including his references to some Mexican immigrants as criminals.

The Trump plan detailed on Tuesday cited $24 billion a year in remittances to Mexico from its citizens in the US, most of whom the campaign said were there illegally.

It proposed modifying a financial provision of an anti-terrorism law to require immigrants to prove they are in the US legally before they can wire money outside the country.

Asked about Mr Trump’s remittances plan, President Barack Obama called it unworkable.

“The notion that we’re going to track every Western Union bit of money that’s being sent to Mexico, good luck with that,” Mr Obama said at a White House press briefing.

“This is just one more example of something that is not thought through and is primarily put forward for political consumption.”

The real estate magnate has dismissed Senator Cruz’s claim he can unify the party, saying at rallies, “Everybody hates Cruz”.