DUBUQUE, Iowa -- Republican presidential candidate Donald Trump has taken on another popular TV news personality, this time a Spanish-language broadcaster who was eventually removed from a news conference.

The billionaire businessman engaged in a prolonged confrontation about his immigration policy Tuesday with Jorge Ramos, the Miami-based anchor for Univision, during a news conference in Iowa.

Trump, who has taken an early lead in the crowded Republican presidential race but remains a longshot for the White House, has already unnerved party leaders with his inflammatory comments about Hispanics. Republican leaders see Latinos, who have voted overwhelmingly Democratic in recent presidential elections, as a rapidly growing demographic critical to their future. Trump launched his campaign by describing Mexican immigrants in the U.S. illegally as "criminals" and "rapists."

Earlier this month he sparked a feud with a popular female TV host, worrying some Republicans that he was damaging the party's image among women, another demographic the party has tried to court.

On Tuesday, Ramos began to ask Trump about his immigration proposal, which includes ending automatic citizenship for infants born in the United States to parents in the country illegally.

Trump interrupted him, saying he hadn't called on Ramos before repeatedly telling him to "sit down" and then saying, "Go back to Univision."

As one of Trump's security detail approached Ramos, the anchor continued to speak, saying: "You cannot deport 11 million people." Ramos was referring to Trump's proposal to deport all people in the country illegally before allowing some of them to return.

As he was taken from the room, Ramos said, "You cannot build a 1,900-mile (3,000 kilometres) wall," another proposal in Trump's plan.

Moments later, Trump defended Ramos' removal, saying: "He just stands up and starts screaming. Maybe he's at fault also."

In an interview on ABC's "Good Morning America" Wednesday morning, Ramos said he was not expecting to be tossed from the news conference.

"Never in my life -- and I've been a journalist for more than 30 years -- have I been thrown out of a press conference," he said.

Trump told NBC's "Today" show that Ramos "stood up and started ranting and raving like a madman. He was totally, absolutely out of line."

The incident happened the day after Trump resumed his feud with Fox News Channel anchor Megyn Kelly. Trump noted Kelly's return a vacation Monday night by tweeting that he liked her show better while she was away. He said Kelly "must have had a terrible vacation" because "she's really off her game," and retweeted a message that referred to her as a bimbo.

Fox News chief Roger Ailes called on Trump to apologize.

Trump has been attacking Kelly ever since her tough questioning of him during the first Republican presidential debate, seen by 24 million people on Fox on Aug. 6. A day after the debate, he said Kelly had "blood coming out of her eyes, blood coming out of her wherever." He was then dropped from a major gathering of conservatives later that week.

Trump's immigration proposal has sparked intense debate within the 2016 Republican field. Several candidates, including former Florida Gov. Jeb Bush, have called it "unrealistic."

Ramos was later allowed back into Tuesday's news conference. Trump greeted him politely, though they quickly resumed their argument, interrupting each other during an extended back-and-forth.

"Your immigration plan, it is full of empty promises," Ramos began. "You cannot deny citizenship to children born in this country."

Citizenship for infants born in the United States is guaranteed by the U.S. Constitution. Changing that would require a constitutional amendment, a cumbersome process in which change must be approved by Congress and then by two-thirds of the 50 state legislatures.

During the five-minute exchange, Ramos claimed that 40 per cent of people in the U.S. illegally enter through airports, not over the Mexican border. "I don't believe that. I don't believe it," Trump responded.

A 2006 report by the Pew Hispanic Center found that up to 45 per cent of the people illegally in the U.S. entered with legal visas which since have expired.

Trump said he did not believe that a majority of immigrants in the U.S. illegally were criminals, or in the country to commit crimes. "Most of them are good people," he said. But he described recent cases where people had been killed by assailants later determined to be in the U.S. illegally.

Trump also repeated his claim Tuesday evening that he would stop eating Oreos, citing the cookie maker's decision to close a plant in Chicago and move it to Mexico.

Trump's claim is partly true. Oreo's parent company Mondelez International Inc. said last month that it will move some production lines to Mexico, but the plant in Chicago will remain open.