Leading Republican presidential candidate Donald Trump said he will deport all illegal immigrants in the United States if he is elected president and rescind all of President Obama's executive immigration orders.

Appearing on NBC's "Meet the Press" Sunday, Trump said, "We're going to keep the families together, but they have to go."

He said even for those illegal immigrants who have no country to go back to, "they have to go."

"We will work with them. They have to go. Chuck, we either have a country, or we don't have a country," he told host Chuck Todd.

The DREAMers program, which the Obama administration has implemented for illegal children brought to the US, should be rescinded, he said, adding that "we have to make a whole new set of standards" for immigrants.

In his immigration policy, Trump particularly targeted illegal immigrants from Mexico, which he said, should pay for the wall at the southern border.

"Mexico must pay for the wall and, until they do, the United States will, among other things: impound all remittance payments derived from illegal wages; increase fees on all temporary visas issued to Mexican CEOs and diplomats (and if necessary cancel them); increase fees on all border crossing cards – of which we issue about 1 million to Mexican nationals each year (a major source of visa overstays); increase fees on all NAFTA worker visas from Mexico (another major source of overstays); and increase fees at ports of entry to the United States from Mexico (tariffs and foreign aid cuts are also options). We will not be taken advantage of anymore," according to his immigration policy posted on his website.

Trump was lambasted by fellow Republican candidates when he accused Mexico of sending criminals and rapists to the US.

Former Florida Governor Jeb Bush described Trump's latest comments on immigration as "extraordinarily ugly."

An estimated 11.3 million illegal immigrants are in the US and more than half are from Mexico accounting for 5.1 percent of the US labour market.

In the same interview, Trump said he would defund Planned Parenthood if it continues to provide abortion services.

He said is opposed to abortion except in cases of rape, incest and to save the life of a mother.