MILWAUKEE - US Republican presidential candidate Ted Cruz has pulled into a statistical dead heat with front-runner Donald Trump, a new Reuters/Ipsos national poll showed on Tuesday, as the Texas senator appeared poised to pick up a key victory in Wisconsin's primary.

US Republican presidential candidate Ted Cruz is joined by Wisconsin Governor Scott Walker, Cruz's wife Heidi, and former presidential candidate Carly Fiorina at a campaign event in Wisconsin, United States, April 4, 2016.  [Photo/Agencies]

Cruz received 35.2 percent of support to Trump's 39.5 percent, the poll of 568 Republicans taken April 1-5 found. The numbers put the two within the poll's 4.8 percentage-point credibility interval, a measure of accuracy. Cruz and Trump were also briefly in a dead heat on March 28.

The US senator from Texas was running ahead of Trump in Wisconsin according to opinion polls as voters in the state went to the polls on Tuesday. Cruz hopes a win in Wisconsin would show he can unite disparate factions of the party and break Trump's momentum.

Trump has led almost continually in national Reuters/Ipsos polling since last July. Ohio Governor John Kasich, the only other Republican still in the race for the party's nomination, placed third in Tuesday's Reuters/Ipsos poll, with 18.7 percent.

Facing possible defeat in Wisconsin on Tuesday, Trump proposed blocking money transfers to Mexico by undocumented immigrants as a way to pressure Mexico to pay for a border wall, a key component of his controversial immigration plan, which has won votes in other states.

Trump's campaign said in a memo that if elected, he would use a US anti-terrorism law to cut off remittances from people living in the United States illegally. The memo elaborated on an idea Trump floated in August, when he suggested seizing all remittances tied to "illegal wages."

Asked about Trump's remittances plan, Democratic 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," Obama said at a White House press briefing.

Cruz has told reporters that only he and Trump can earn the 1,237 delegates from the primary contests necessary to win the nomination outright or to survive a contested convention.

Cruz's support in Reuters/Ipsos polling rose as Trump's wavered, particularly among women, after recent missteps.

Trump said in a March 30 interview that if abortion was illegal, women who end pregnancies could face punishment. He later reversed himself to say doctors who provide abortions should be held responsible.

More than 70 percent of likely women voters said they had an "unfavorable" opinion of Trump, according to a rolling poll average for the five-day period ended April 5.

In the Democratic race, US Senator Bernie Sanders of Vermont has a slender lead in opinion polls in Wisconsin over front-runner Hillary Clinton, but she maintained her lead nationally in a Reuters/Ipsos poll also released on Tuesday.