United States President Donald Trump has revealed plans to terminate the right of citizenship to babies born in the country to immigrants and non-citizens.

Key points: Mr Trump is pushing a hardline immigration policy to win votes in midterm elections

Mr Trump is pushing a hardline immigration policy to win votes in midterm elections The 14th Amendment guarantees the right for children born in the US to receive citizenship

The 14th Amendment guarantees the right for children born in the US to receive citizenship Revoking birthright citizenship would raise questions about a president's authority to make changes to amendments to the constitution

Speaking to Axios on HBO, Mr Trump said he was seeking legal counsel to determine if he was able to bypass Congress to change the constitution and end birthright citizenship through an executive order.

"They're saying I can do it just with an executive order," Mr Trump said.

He added the false claim that "we're the only country in the world where a person comes in and has a baby, and the baby is essentially a citizen of the United States".

At least 30 countries offer birthright citizenship through the principle of jus soli or the "right of the soil", including Canada and Mexico.

This principle was abolished in Australia in 1986, conferring citizenship status only to children born to at least one parent who is an Australian citizen or permanent resident, a principle known as jus sanguinis, or "right of blood".

'You obviously cannot do that'

US House Speaker Paul Ryan says that President Trump "obviously cannot" revoke birthright citizenship by executive order. ( AP: Julio Cortez )

Revoking birthright citizenship would spark a court fight over Mr Trump's unilateral ability to change an amendment to the constitution.

In an interview with US radio station WVLK, House Speaker Paul Ryan rebuked Mr Trump's comments.

"Well you obviously cannot do that. You cannot end birthright citizenship with an executive order," he said.

The 14th Amendment guarantees that right for children born in the US.

The first line of the 14th Amendment states: "All persons born or naturalised in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside".

The US Supreme Court has never ruled squarely about the clause's application to children of immigrants who are in the country illegally.

Mr Trump did not make a distinction between legal and illegal status in his remarks.

An 1898 Supreme Court decision held that the US-born son of legal Chinese immigrants was a citizen under the 14th Amendment; a footnote in a 1982 decision suggests there should be no difference for children of foreign-born parents, whether they are in the US legally or illegally.

Hardline immigration policy push ahead of midterms

Mr Trump has intensified his hardline immigration rhetoric heading into the midterm elections on November 6.

Along with his comments on birthright citizenship, he has stepped up his warning about the 7,000-strong migrant caravan travelling from Honduras to the US and deployed 5,200 troops, including armed soldiers, to confront them at the Mexico border.

"Many Gang Members and some very bad people are mixed into the Caravan heading to our Southern Border," Mr Trump tweeted on Monday.

"This is an invasion of our country and our military is waiting for you!"

Last year Mr Trump rescinded a program that allowed non-citizens who arrived in the US as children and had grown up in the country a pathway to citizenship, known as the Deferred Action for Childhood Arrivals.

The people who qualified for the program were collectively known as the Dreamers.

Sorry, this video has expired Migrants trek under Mexico heat en route to US

ABC/AP